[johnhiler]

That site is _ck_’s developer showcase… I believe she did those flags with mini-track:

https://bbpress.org/plugins/topic/mini-track/

She no longer officially supports that plugin though – much of the functionality has been moved into the excellent mini-stats:

https://bbpress.org/plugins/topic/mini-track/page/3/#post-2436

But the flag functionality isn’t part of mini-stats, alas.

If you know how to edit or develop WordPress plugins, you shouldn’t have a problem working with bbPress plugins! If not, then maybe you could hire a developer to help with the port…