'Thread closed' but is it?

[GiddyOnZackHunt]

The Anonymous MIL thread. After Iona's closed message I noticed that some posters had successfully commented. I tried to say "Surprised it's still here" and got "This thread is closed". Ten minutes later another post appears so I try again with the same result.
Do some posters (night watch?) have permission to post on closed threads or is it an app/desktop/mobile site issue? And if it is a permissions thing should it be so obvious?

[CountBeculaMumsnet]

Hi GiddyOnZackHunt - thanks for flagging this. Tech are currently looking into why this happened. We'll update when we know more.