This is a somewhat trivial bug, but a bug nonetheless. It sometimes happens that one starts editing a comment, and then upon submitting the edit one gets an error message that the comment can only be edited for five minutes. If one then immediately tries again to submit the edit (don't ask why one might want to do that, I just clicked again without thinking), one doesn't get the same message again but the message that says that comments can only be edited once every five seconds. That doesn't feel right; it seems to suggest that you can successfully submit the comment if you wait for five seconds, which of course you can't because you'll then get the five-minute message again. The five-minute message should be consistently displayed in this case.
While I agree with you completely, this is not a trivial change in our code.
The 5-second limiter is a particular type of throttle whose order of operation is always first to help prevent denial of service attacks.