I particularly love the suggestion to use https://ideas.mozilla.org/ to submit feedback, as if that change went through the same procedure, and as if they didn't moderate away any suggestion that they don't like.
And yet they still don't realize that this "we know better than the users what's good for them" attitude is killing their product.
They could've kept ten percent forever if they didn't forsake the things that made Firefox great in the first place and the people who loved them for it. Now they've thrown that away and along with it any chance to avoid irrelevancy and extinction.
You can find multiple people who would describe anything as broken. I'm several dozen comments into that thread and I still haven't found a single person even attempting to explain why the old functionality is needed beyond "I don't like using my `?` and `Ctrl-K` keys", which Mozilla absolutely should not have dignified with as much time as they gave it.
The person arguing that the entire search box should just be removed if it isn't actually any new functionality has a point, but that's somewhat tangential to the "bug" they're describing.
Whether using ^K or ? is better or worse is entirely besides the point.
Normal yes, reasonable no. It's a problem that solves itself extremely quickly if you just learn to accept it. It's mildly annoying for a few days and that's it. Sure, let's not go breaking muscle memory willy-nilly just for the sake of it, but you can also go too far in the other direction: https://xkcd.com/1172/
In this case there's no downside at all beyond "I hate change", and opening a bug report is way more effort than just getting used to that.
I think the main problem is that Mozilla consistently underestimates just how much people hate it when their software changes behaviour in surprising ways, and also how little control they give to users over these kind of changes.