Can a small countdown slide-down (like the "you have x answers and y comments thing") be provided to indicate how long before another comment/comment upvote/etc. is allowed?
I've never gotten rate-limited on voting. I have been hit by the 30-second comment rate limit (I type very quickly -- well over 100wpm), and the 5-second comment upvote limit, but ... I just wait.
This is going to sound harsh, but long ago I learned to count to 5 and 30. (Admittedly, it is harder for me to count to thirty, as even after I take off my socks there's still not enough digits. Luckily, by the time I usually manage to remember that, the whole thirty seconds has passed.)
For comment votes (which also include flags), just take a couple deep breaths and you're done. For comment limit itself, if it's really bugging you, pop a new tab and open up a random Wikipedia page. By the time you get about halfway through the piece, your new comment will be more than ready to post.
Or, you know, limit your own activity. It's not necessary to upvote every comment nor add a comment to every discussion.
I guess I see why you would want this, but have you ever seen a website with all kinds of countdowns on it? If there was counters for comments, voting, etc., I think it would just be confusing and cluttered. This is not a race or anything and you are not bidding on anything like ebay.
The constraints are there to help combat spam/bots and to maintain maximum site performance. Just seems a little more hassle/clutter than it is worth.