Until some time ago (a few weeks or so), I'm pretty sure I could still come across comments written by users I blocked. I know that because I started to tag the users because of that. Now I've noted that not only comments by blocked users are completely hidden from me, but the entire thread starting from them, including responses by other users, is invisible.

I'm not really sure if that's the intended behavior (and if it's piefed or my instance that does it).