I have just clicked to monitor the thread and then switched to another user and posted a test post and I got an email notification.

Looking in our CC mail account no notifications have been sent for this thread since the 15th August.

So I do think that it has something to do with the thread being moved.

Thanks for the report. I can explain the issue as expected behaviour... initially they would have been getting comment topic notifications, then when it was moved, it would no longer be a comment topic. Composr topic notifications and comment topic notifications are different, although Composr works to make sure that if something is a comment topic, normal topic notifications do not happen.

We could convert the comment topic notifications into normal topic notifications, upon moving; however it'd be a fair amount of code to do it, and it's very much a corner use case. I will open a separate public tracker issue for it, which I imagine will just sit there, but I think it is worth having a presence on the tracker if just for awareness.