It happens on the incredibly rare occasion now and again.
I wouldn't say it's incredibly rare. Continuing with the example of the Halo 3 review thread, across the first three pages (at 50ppp) there are no less than 16 perma-banned members, and of those 16:
- Odysseus logged in ~a month after his/her last post
- Hitler Stole My Potato logged in ~five months after his/her last post
- EverSoTrendy logged in ~eight months after his/her last post
- LM4sure logged in ~a year after his/her last post
- Stoney Mason logged in ~five months after his/her last post
- devilscallmedad logged in ~four years after his/her last post
- Karma Kramer logged in ~four months after his/her last post
- RumFore logged in ~six months after his/her last post
- Mandrion logged in ~10 months after his/her last post
- OokieSpookie logged in ~nine months after his/her last post