Damage

• All odd-numbered damage effects that are halved on a successful save deal +1 damage.
• Any effect that halves odd-numbered fall damage deals +1 damage.
• Any effect with a value based on odd-numbered half damage dealt or healed results in +1. These are unaffected by any tweaks to resistance/vulnerability.
• Examples: Guardian's Cause Harm, most damaging effects with saving throws, Evasion features from monk, operative, sentinel and Hunter scout, operative's Explorer's Exploit, sentinel's Ideal of the Steadfast, Aggression sentinel's Living Current, Mounted Mastery, Soresu form, operative's Uncanny Dodge.
• Note: Resistance, to my knowledge, is the only feature that was changed to compensate for the new rounding rule, but did so by adding an extra step to the simple equation involved in resistance instead of adding "(round down)" to it. This also means resisted damage deals half damage rounded down, functionally, while all other halved damage is rounded up.

Hit points

Any healing or temp HP effect based on half damage dealt, half HP restored, half max HP, etc., will get +1 if the starting number is odd.

• Examples: Two of Sage consular's healing features, Armstech engineer's Power Loop, Assault fighter's Survivor, the DC for all Constitution saving throws to maintain concentration.

Proficiency bonus

I know "equal to your proficiency bonus" class abilities are being changed to flat values unreliant on prof bonus, but round-to-the-nearest may affect them depending which rules change comes into effect first, or if the flat values change isn't made to all of them.

• Examples: Two of scout's Routines, sentinel's Led by the Force, having "training" in anything Assault fighter's Remarkable Athlete, Gambler scholar's Blind Luck, the Power Channeling feat.

Ability score modifiers

Anything that grants a bonus based on half a character's ability score modifier gets +1 if the modifier is an odd number.

• Examples: scout's Sharpshooter's Routine, sentinel's Ideal of the Artisan, Niman guardian's Enlightenment, monk's Vow of Serenity, Balance consular's At-will Barrier regeneration maximum, Politician scholar's Motivating Diplomat, Aggression sentinel's Voltaic Slash, Forceblade sentinel's Phase Throw, the Force Guidance feat, Djem So and Shien forms, -1 carrying capacity for Tiny creatures.

Class levels

Anything that is a bonus or has uses based on half the character's class level now gets +1 on odd-numbered levels.

• Examples: Consular's Force Recovery, guardian's Aura of Conquest, sentinel's Ideal of the Vigorous, Warchief berserker's Inspiring Presence, Suggestion consular's Delayed Effect (+1 round available), Gadgeteer engineer's Physical Barrier, Heavy Weapons fighter's Maximum Output, Beguiler operative's Enthralling Vigor, Forceblade sentinel's Forceblade Mastery

Group checks

When making group checks, half must pass checks for the whole group to pass. For odd-numbered parties, the requisite number of passes increases by one party member. (So before, in a party of 5, 2 characters had to pass a group check for the whole group to pass. Now, 3 must pass, or the group fails.)

Long rests

Characters with odd numbers of hit dice regain +1 die on long rests.

Speed, Credits and Time

The rule effect on speed, movement, and any sort of physical measurement isn't of note, because many tables treat half a foot as a valid unit of measurement anyway. The same applies to anything that halves time or credit values

Equipment

• Rigid property adds +1 to Dex saves if your Dex modifier is odd.
• Absorbing property costs +1 tech/force point--and the damage taken is increased by +1--if the damage dealt is odd.
• Elongating property increases the cylinder radius by +1 foot if the elongating number is odd.
• Extending property does the same for its line width.
• Repelling property increases its DC by +1 if your proficiency bonus is odd.
• More "half damage on successful saves", +1 if damage is odd.

Archetypes

• Confluence consular's Manipulate Life Force gains +1 temp HP (level)
• Negation consular's Power Surge and Conflux deal +1 damage (level)
• Astrotech engineer's Ionizing Field deals +1 ion damage (level)
• Astrotech (companion) can install, replace, or remove +1 droid traits during a long rest (Int mod)
• Audiotech engineer's Potent Amplitude DC to maintain a song is +1 (damage taken), and its Support Crescendo lets it take +1 damage (damage taken)
• Biotech engineer's Overclock Body can contribute +1 HP and max HP to cover the cost of tech powers (power level), its More Machine Than Man lets it take +1 damage (damage taken), and its Mighty Prowess Enabler adds +1 to attack rolls taken (prof bonus)
• Construction engineer's Portable Structure can restore +1 HP to structure (structure's HP)
• Cybertech engineer's Adaptable Applications adds +1 to damage or healing with a tech power (level)
• Enhancement fighter's Quell Shot halves a target's damage it can deal for a round, but it would deal +1 if it deals odd-numbered damage
• Exhibition fighter's In the Spotlight deals +1 damage to a marked target (Charisma modifier), (irrelevant past lv18, but this changes to +1 to attack rolls at the same level)
• Fireteam fighter's On Your Six and Tactical Advice give +1 AC (prof bonus)
• Mounted fighter's Unwavering Mark deals +1 damage (level)
• Aqinos guardian can install, replace, or remove +1 droid traits during a long rest (Int mod)
• Jar'kai guardian's The Way of the Acklay deals +1 damage (Str/Dex mod)
• Trakata guardian's Master of Deception has enemies take +1 damage from their own attacks (damage enemy deals)
• Ysannanite guardian's Phasestorm adds +1 damage when rolling below half the maximum (damage die roll) and its Master of the Unorthodox lets it do so +1 times (Wis/Cha mod)
• Kro Var monk's fire weapon deals +1 damage (focus ability mod), and can use their Elemental Master features +1 times (prof bonus)
• Teras Kasi monk's Forredari Dance deals +1 damage (level)
• Saboteur operative can install, replace, or remove +1 tracker droid traits during a long rest (Int mod)
• Chef scholar's Allergens subtracts +1 to enemy d20 rolls (superiority die roll)
• Explorer scholar's High Ground grants +1 damage (Critical Analysis ability modifier)
• Geneticist scholar Mutagenic Analysis adds +1 to saving throws (CA mod), its Mutagenic Transformation grants +1 AC (CA mod), and its Mutagenic Hardiness grants +1 temp HP (level)
• Artillerist scout can install, replace, or remove +1 turret traits during a long rest (Int mod), and its Crisis Management gives its turret +1 to saves (prof bonus)
• Illusionist scout's Charged Illusions deals +1 energy damage (level)
• Mastermind scout's Adaptive Techie can replace +1 tech power (Int mod)
• Mechanist (companion) can install, replace, or remove +1 tracker droid traits during a long rest (Int mod)
• Teleportation scout's Mark of the Teleporter deals +1 damage (damage die roll)
• Synthesis sentinel's Reflective Shield deals +1 ion damage (damage taken)

Species

• Colicoid's Defensive Ball gives +1 AC (prof bonus)

Levels, Proficiency Bonus, and Modifiers

Most of these are specific effects getting +1 to a minor value a level earlier than they would have, or a few levels earlier if based on proficiency bonus, but being unchanged otherwise, and not affecting max level players for the most part. Those effects based on ability modifiers deserve a closer look, as these are harder to increase, and when their scores cap at 20, their modifiers of +5 when halved become 3 instead of 2. This is a more significant buff than the former cases, and remains persistent on max level characters, but almost all of these are characters getting buffs, in the end.

Damage

Damage-based features are more widespread and are going to be harder to get used to, but generally balance themselves out. All "half damage on a successful save" features have been given +1 when the damage is odd. This applies to damage both taken and dealt by players, so that could be seen as balancing out.

However, a change was made to resistance already that counteracts this same effect Round Appropriately would have had on it, albeit by adding extra steps to the resistance equation. Furthermore, half damage on successful saves and resistance are not the only cases where damage is halved in the game. By making an exception for resistance but none of the others, damage that is halvd by resistance now deals less damage overall than damage that is halved any other way.

For example, before the rule change, if you would take 13 damage, but it was halved by any effect, you would instead take 6 damage. Under the new rule, resistance still reduces this to 6 damage, but all other effects that halve it instead reduce it to 7. Between resistance's equation being extended and different halving effects resulting in different damage amounts for the same amount of original damage, taking half damage has now been made much more complicated.

Proficiency Bonus vs Set Levels

Some archetypes get increases to their features based on their proficiency bonus. Some of these have already been changed to instead increase at set levels. Because this happened before the Round Appropriately change, their levels are still based on Round Down. And if later features also get reworded to be fixed instead of directly based on prof bonus, then their set values would be based on Round Appropriately, alongside the Round Down-based ones. I don't know what to make of this, but it's potentially awkward, so I wanted to point it out.

Rounding Verbiage

Of major concern, from my point of view, is not necessarily the rule change itself, but something that accompanied it in the Reddit post. "All verbiage regarding round up or down in class features has been removed." Oddly, anything that said "(round down)" was already redundant anyway, because it naturally already would. Similarly, "(round up)" becomes redundant with the new rule. However, the wholesale removal of any and all of them is something to reconsider, particularly for the following.

• Group checks, I already covered, but parties of 3 or 5 shouldn't need to have one more person pass a given check for the others to pass.
• Concentration checks are already a discouraging factor in power selection, and this change makes it easier for them to break. Unlike the halved damage increase, this change mostly adversely affects players, since so few monsters concentrate on anything. A Con save to maintain concentration has a DC of 10, or half the damage taken, when damage is taken. This means odd damage past 20 raises the DC by 1 above what it was before.

Nerfs

While most of these changes slightly buff a lot of class and archetype features, some select few archetypes have had features nerfed by this. If the intention of the rule change is to be a buff, then maybe these are unintentional consequences deserving of a closer look.

• Quell Shot on Enhancement Specialist fighter afflicts an enemy with a condition where it deals half damage with its attacks for a round, but this would be mitigated by the rule change.

Some positives

• All techcaster archetypes gaining +1 tech points on odd levels, including the levels they start out as, is a good thing, in my opinion. These archetypes have historically been strangled for casting ability, so this could be a step in the right direction. In fact, looking through older versions of them, it seems this has been a change that's been slowly being pushed for them individually, and now it's complete for all of them.
• Droid/turret companions being able to swap out more traits is cool.
• Way of Technology consular's Ionized Weave feature still says to "round down" when listing its cost to force points. This is not only a good call to avert nerfing it, but shows that some features can still be rounded down where appropriate.