This is not an important bug to fix, but just noticed it today. You normaly get the 5 seconds between comment vote warning when you try and vote for too many comments at once. I deleted two of my comments back to back on the same question and I got that same warning
You can replicate it by making two comments and then delete them both quickly.
Like I said, not important to fix anytime soon, but noted.
Deleting a comment counts as a 'vote to delete'. That being said it only takes one vote, and your own.
Just to verify that I'm not lying, deleting a comment is
VoteTypeId = 10 //(http://meta.stackoverflow.com/posts/comments/###/vote/10)
Here is the list of vote types, where 10 is clearly marked as deletion. Normal up-votes have a type of 2. So the message is correct, you're limited to 1 vote every 5 seconds.