Downvotes are not indicated in comments with only one exception. When it becomes too low rated it must be clicked to be shown.
Usually after it receives -3 comment ratings much as many of yours have been. Even upvoted comments can have this happen to them. But the difference is still 3 more downvotes per amount of upvotes. So, a 0 vote comment needs 3, 1 needs 4, 2 needs 5 and so on.
It's not really that big of deal but they can hurt your overall comment posting reputation; and get you a freeze on your account if you receive too many downvotes in a short amount of time. This is a timed penalty, however, to prevent people from abusing the comment reputation system.
Not that people still don't try and do that.
Does that help you?