Is the Raspberry Pi forums shadow banning users?

I have no messages that I am banned but I can’t log into my account there?

What happens when you try to log in?

Not something I’ve experienced and I’m able to log in fine, but does seem very heavily moderated

I’m a member of that forum. I’m not happy with how its moderated but its there forum. I haven’t gotten any warnings for anything I’ve posted. They just lock any thread they don’t like with no real warning or reason why?
You should be able to view the forum even without being logged in. Then just search for your username and check the profile. If your banned I would think it would show it there.
Or have a look see at a post you made in a thread. You would have a banned banner somewhere by your avatar.

There is nothing which says I am banned but I can’t view my profile.

There is a contact us link at the very bottom of their forum page. You could try that.