If I remember correctly it's to prevent a softlock somewhere (in DDG1 donuts simply doesn't come back, but they need to in DDG2 because of the multiplayer component, so every section where you can use donuts to descend into a lower area needs to be escapable from below too and solid donuts turning into regular donuts guarantees that)
6 days ago(+1)
You mean donuts don't come back. :P "Does" is only for third-person singular nouns in present tense, and "donuts" is plural.
I will say, I'm having trouble seeing how players can get stuck in multiplayer without getting stuck in that same spot in single player, but I guess I'll take your word for it.
Anyway, here's another that I noticed a few days ago or so: the diagonal whip has a much-thinner hitbox than the horizontal whip. This is easiest to notice while trying to clear away the green skeletons' fog from a standstill, which is significantly harder to do diagonally:
You can tell by the skeleton's throwing animation that the top image isn't the fog disappearing on its own because of when those animations happen relative to each other compared to when they happen in the bottom image, where the fog *does* disappear on its own.
5 days ago(+1)
Noticed another small typo: the description for the knockback accessibility option says "attacks knocks" when it should just say "attacks knock" without the last s.
2 days ago(+1)
A bit more feedback: I like how the powerup-loss effect happens when the player is only one hit away from death (or two hits for certain weak enemy attacks or high-HP characters), as it functions as an in-your-face warning that you're about to die and should be more careful. However, there's no such warning during boss fights, where the player is immune to losing powerups; it's just the same as every other taking-damage animation until suddenly you're dead. The most that happens is that your tiny health bar in the distant corner of the screen subtly glows red. It'd be nice if you could add some type of more-obvious low-HP warning for those situations as well.
I only just now discovered that Holy Cow's illumination orb also doubles as an attack that can hurt enemies (I was under the impression that it was ONLY for "lighting the way" and the sky lasers were her only offensive spell), so whenever you go to reword their descriptions like I suggested before, I'd appreciate if you made this detail clearer as well.