Do not allow to repeat same comment again and again. See the below image as example case.
There's an idiom: "give 'em enough rope".
Someone who lashes out like this does little harm to anything (I'm guessing it's easy enough to clear up) and is clearly visible.
Removing this outlet means they might concentrate on other forms of anger, which might be harder to spot and harder to clear up.
5 seconds is, for a few of the faster typists here, a bit frustrating. (Not me, I'm just 50 wpm.) Allowing them only 1 comment per minute would not be fun.
Perhaps limit the comment rate for people with less than X reputation? But only if this is actually a problem.
I recently saw that actual question on Stack Overflow. He did this "masterpiece" because the community (some users) closed the question for being an exact duplicate.
The problem is that I see more and more of this these days. It is really irritating for me as well.
A solution could be to limit the user to submit one comment every minute. 5 seconds are nothing. If everyone would post a comment every 5 seconds, Stack Overflow would be an uncontrolled chat room. Also the hosting would cost more as well :)
Summary: Increase the time between two comments to stop spam and dups.
Or there could be another more efficient and intelligent way of doing this. You could make the time limit proportionate to the user's reputation. Like:
If someone has 20k+ rep - the time limit is 3 secs
10k+ rep - 5 secs
5k+ rep - 10 secs
2k+ rep - 15 secs
1k+ rep - 20 secs
500+ rep - 25 secs
100+ rep - 30 secs
15> - 60 secs
Maybe this would be a more interesting and safe solution. Just an idea though...