If you upvote a comment and then immediately retract that vote, you get this error if you do it too quickly:
You may only submit a comment vote every 5 seconds.
Aside from the fact that I'm not submitting a comment vote, but rather retracting it, the primary and only use case is to undo a misclick immediately after it happened, such that you only have a 60 second window, and not even that if you reload the page.
5 seconds isn't a huge deal, but it makes no sense to put a 5 second timer there if the user is expected to undo it immediately, if at all.