I agree with post1

Why hasn't that been added yet any way.

Honestly if I had a pound in money for every time someone has mentioned this I'd be pretty well off, where as if I had a pound in weight  for every time someone mentioned this I'd be pretty well built .

The lack of pm notifications is just as confusing to me as to everyone else, and yet there are neither installable extensions nor anything in the admin settings related to them, indeed if adding them was a simple matter, we would've done so years ago.

what is doubly confusing, is that the project.aon forus also use PunBB and yet do show number of unread messages on the main page, so goodness knows.

I don't know, since I haven't used the project.aon boards for quite some time and I'm not %100 sure who the webmaster is, but its probably worth a go. That is of course assuming that they actually do use PunBB, rather  a bb system which just looks very similar.

Oddly enough I do sort of remember that back when the pm system was first introduced in 2011, it did have the same notifications that project.aon did, showing "you have x messages" instead of the private messaages link at the top of the page, , then a couple of weeks after it changed to the current system.
I did wonder when I looked at the admin pannel if there was an obvious setting that had been turned off, but I combed the admin settings for quite some time and couldn't find anything.

Isn't anyone able to code it, I don't know that it would even be all that difficult for someone with a modicum of PHP knowledge.