Sorry, but that's precisely how reddit works. If someone blocks you - all you see is [unavaliable] when they post.

There are subreddit bans which warn you before you waste time typing, and I’m pretty sure if a comment is removed you can still recover it to copy and paste.

This is true (unless it's removed by reddit), but this is just the difference between how activitypub works vs. reddit so far as I know.

If blocking someone on reddit works the same way, maybe it’s not a problem because the front page of every subreddit I’ve ever been on has zero posts from the kind of people that block a good contributor like me.

Reddit is massive. I have no idea how active you are on there, but the likelihood of you finding a poster on the frontpage of a subreddit that has blocked you is marginal.