Comment labels serve multiple purposes overall. Tildes has no downvoting, but some labels can effectively act as "downvote with a reason". Labels will also make it possible to support various methods of filtering comment threads, such as both "show this thread without jokes" and "show only jokes from this thread".
Overall, voting on a comment should mean something like "this is a good comment and I think other people should read it", while labeling a comment adds more information. With the combination of both, you can express things like "this is a good comment, even though it's off-topic", and "this is a joke, but it's a good one".
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I don't really like this habit Tildes has of minimizing comments if someone marks them as 'noise', it's effectively another way of downvoting
https://docs.tildes.net/mechanics#comment-labels
If you have feedback about a feature, you might want to post a topic in ~tildes to discuss it.