[fmx]

Here is another good one: too easy to hit CTRL+Q instead of CTRL+W https://bugzilla.mozilla.org/show_bug.cgi?id=52821

Only 20-and-a-half years to fix that one! In this case it wasn't because nobody got around to it, but because people could not agree on the fix, even though more or less everyone agreed that the old behavior was bad.

[Twirrim]

There is a browser.warnOnQuitShortcut setting in about:config, that can have it pop up a nice warning and stop you accidentally ctrl+q'ing firefox. I don't know if they've gotten around to making that the default for new profiles. That bug thread is a irritating mess of conversations.