Say I am interacting with user abc in a comment chain. If they start acting incendiary and I block them, I can no longer see abc's comments. This would be fine, except... if user xyz responds to one of my comments in that comment chain, I have no way of interacting with that. Want to reply? Want to block them, too? Too bad, the entire chain is invisible (but you're still notified about xyz's comment, which you can do nothing about).

Maybe instead of making abc's comments invisible, they could be replaced by a comment box with "blocked user" instead, so the rest of the comment chain remains intact?