I don't comment in the comment section either, but I sometimes read it and I often see people accusing the channel of deleting comments, and the responses from the channel owners that they don't delete any comments. And these channels don't even have anything to do with politics or any controversial topics.

I sometimes comment in the live chat on livestreams though. I'm sure there is some kind of super clever and sophisticated algorithm to filter out comments, but in practice as far as I can tell, what comment in the live chat gets through is virtually just random.