Let's say the party had two Lore Bards, and both used Cutting Words on a creature who tried to attack.
Does that stack, since they are separate penalties and not enduring effects (like bless)? Or would it still fall under the "same name features don't stack" rule?
The rules on stacking/combining game effects states (page 252):
[W]hen two or more game features have the same name, only the effects of one of them — the most potent one — apply while the durations of the effects overlap
I would argue that modifiers to rolls do not actually have a duration and so they cannot actually overlap, so the clause about stacking effects won't apply.
This is similar to the answer to a related question about simultaneous fireballs which argues that you would take damage twice because the spells (and their damage) are instantaneous effects without duration.
Similarly the modifier of Cutting Words does not have any sort of persisting effect that you could call a duration, it simply happens. The modifiers do not have any sort of duration whatsoever, so they cannot overlap. Thus the rules on overlapping effects do not apply and the two uses of Cutting Words will stack.
The Essentials Kit (page 3) states:
[...] When two or more effects have the same proper name, only one of them applies while the durations of the effects overlap (a duration is a time span of 1 round or more). The most potent effect--such as the highest bonus--is the one that applies, or the most recent effect applies if the effects are equally potent. For example, if bless spell is cast on you when you're still under the effect of an earlier bless, you gain the benefit of only one casting.
Because Cutting Words does not last for "a time span of 1 round or more" the rule on effects with the same name cannot apply. Thus they stack.
No, the rule for Combining Game Effects says that s of the same name don't stack effects while they overlap.
“Different game features can affect a target at the same time. But when two or more game features have the same name, only the effects of one of them—the most potent one—apply while the durations of the effects overlap. For example, if a target is ignited by a fire elemental’s Fire Form trait, the ongoing fire damage doesn’t increase if the burning target is subjected to that trait again. Game features include spells, class features, feats, racial traits, monster abilities, and magic items. See the related rule in the ‘Combining Magical Effects’ section of chapter 10 in the Player’s Handbook.
Similar to the fire example, Cutting Words reads:
you learn how to use your wit to distract, confuse, and otherwise sap the confidence and competence of others.
You shouldn't be able to become "more distracted and confused" on a single attack.
Now, Cutting Words doesn't have a duration, but in the case of cutting words they are happening at the same time, so they are clearly over lapping as they are both happening when the attack is happening (not just same round 6 seconds, but as the effect is landing). It would be hard to argue that they aren't happening at the same time as they are both reactions to the same split second action.
