“Properly” blocking people (not allowing them to reply to your topics) is detrimental to discussion.
I understand that some people might have toxic attitudes, but that’s an exception that the admins on the site should handle.
If the admins on the site don’t handle problematic users, then no amount of software engineering is going to fix the problem.
Discourse gives admins plenty of tools to handle that. Discourse also gives users the option to mute/ignore other users like mentioned above.
We have no plans for allowing users to prevent other users from replying to their topics.