We will be evolving the blocking experience so that it not only removes a blocked user’s content from your experience, but also removes your content from their experience—i.e., a user you have blocked can’t see or interact with you.
Previously, if I blocked u/IAmABlockedUser, I would not see their content, but they would see mine. With the updated blocking experience, I won’t see u/IAmABlockedUser’s content and they won’t see mine either.
Like I've said in the other comment, not entirely sure on whether replying was possible since I've never been blocked myself.
To clarify, a few years ago, the blocked user could not see the message either.