I tried to leave a comment similar to the following:
@User: Stuff. @All: Things.
Naturally I got an error popup telling me I can't @notify multiple people. I quickly removed the second
@ and tried to submit the comment again, resulting in:
You can only post a comment every 5 seconds; timer reset
(Exact wording may be slightly different).
The problem is that the first version of the comment wasn't actually posted due to the error. The delay is unnecessary in this case and pretty frustrating (for something that only lasts 5 seconds :P).
I believe I've also encountered this in other situations, but my memory is imperfect and I can't really test it. Something to do with flagging and commenting, I believe.