Very highly upvoted, very wrong answers get very deleted. We have one precedent for this and it was a rather uncontroversial callit was a rather uncontroversial call.
It's simple to see why: we're spreading misinformation and that's not cool. This should never happen, but occasionally it does, and when it does happen we don't really have anything else we can do about it.
This isn't the case, however: the answer is not wrong to the extent that Gnome's post was. There is no reason to resort to such exceptional means.
The community rightly felt that the advice was dangerous to rely upon, so we wanted to stick a warning somewhere. I moved the warning and put it to the question so that, no matter what happens, the warning will appear in the page before all answers. In an ideal world I would've put it in a custom post notice, but I can't do that, so it's in the question body itself. Several answers to the question do, after all, agree that Alt-F4 is safe to use, and it would be silly to stick a warning in all of them, let alone just one of them. I also added a few particular cases that I felt were not addressed by any of the existing answers.
I hope this resolution addresses everybody's concerns.
