Comments are arguably even more important than the code. This is a wonkass move.
Certainly almost every comment on hacker news hasn't understood the change
You can make comments directly on commit objects in GitHub, almost nobody ever does this. You used to see these comments appear PRs (but couldn't reply or resolve them) but now you don't. Nothing has changed with actual PR comments, or code comments, or anything that most people actually use
Parent commenter and several others said they found it very valuable. People seem to want this. Feels like enough of a reason to not remove it for all users with no heads up.
The use case I do see sometimes is having a pull request made up of distinct commits which are each commented on, but that's already a bit of a poor UX in GitHub, easily worked around, and is pretty uncommon.
I mean what is your suggestion to OP? Putting their head in the sand and acting like Github didn't remove a feature they in fact had removed? It's a very niche feature (so much so that more comments seem to misunderstand the feature than actually miss the feature) so the chance of Github not removing it is fairly low even if complaining causes them to delay it a bit.