I had to block a few users yesterday. Today, I noticed about ten notifications from users I've blocked—they replied to me, continued to make up lies about my heritage, and I continued to see their comments in my notifications.
It seems that the only effect of my blocking them is that I can no longer see their comments in context—although I am still notified of their harassment. This is quite the opposite effect from the one I was going for—I mean, I'm happy to spend less time engaging with them, but the block feature seems to be guaranteeing these bigots the "last word" and preventing me from even reporting them. They can then follow me anywhere on kbin and continue to harass me, the block function is only stopping me from doing anything about it.
At least one of these users is on the same instance as I am, kbin.social.
If someone continues to harass you after you've blocked them, it's because they're lonely and want your attention. I've found that offering comforting and condescending words while reverse spamming them with Eleanor Rigby seems to end the harassment quickly... especially when they realize that they can't block you properly either.
Notifications from blocked users is a bug. There isn't really anything that can be done about the "last word" thing, though. On reddit-style platforms, the expectation is that blocking a user just hides their posts and comments. If the blocking user's activity was hidden from the blocked user, then it would be possible to preemptively block someone before defaming them in order to stop them from reporting it.
I may be mistaken on the exact details of how it works on reddit, but allowing non-moderator users to prevent others from replying doesn't sound like a good idea. For comments, preventing a blocked user from replying directly in a child comment means they'll just reply in a sibling comment instead. They still get the last word, so the only thing accomplished is to mess up the threading a little bit.
For posts, preventing blocked users from replying gives the poster pseudo-moderator powers over replies. They can block anyone criticizing or disagreeing with them, giving them significant narrative control. Not exactly desirable.
Blocking should only be for filtering what the blocking user sees. It cannot be a substitute for proper moderation.