Currently, the comment vote limit is one every five seconds. I suspect it's a common behavior to read a discussion in comments and choose to upvote more than one comment after reading the whole discussion. This can become a little annoying to wait 5 seconds for every upvote.
My proposal is to change the limit from one every five seconds to something like six every 30 seconds. This way, the user experience will improve without any effective changes to the current comment vote limit.