I don't like that. If the user cannot be held liable for whatever reason it needs to fall on the site. I don't like that people can be harmed without recourse. There is little incentive for the site to run communities that aren't toxic.
There's little incentive for good moderation, and there's little cost for any moderation, which makes sites business models work.
I agree with you that it has gaps and ugly side effects, but it also has the effect that a lot of things are working because you're not by default responsible for them because they've been commented on your server.
