Thanks for that and - as is often the case - I was only half-correct in the first place.
If you find a post from a Banned Member that's still visible, you can click on their name and see the details of the ban. So I was wrong to say that something has changed. Sorry about that!
The REAL issue I had was that Banned Members do not appear on the Full List of Members. I'm not saying this is wrong - either in principle or logistically - but it makes things harder. I've just used our old contributor 'Igor' to confirm it.
So a couple of days ago, I got in a bit of a spat with a newbie. I came back to the thread to find his posts had disappeared - making my own reply look a bit odd without them. I just wondered whether he'd been banned and, if so, why and for how long. But with his posts gone, I couldn't check using those. I looked at the list of members but couldn't find him. So I guess that's the simple answer: "If they ain't on The List, they ain't coming in".
It's not a problem - as I said initially, I just wondered what was going on.