Clearly defined rules means you that you wouldn't get situations like the one that just happened....but you're basically saying "you'll get denied if we feel like it" since sometimes it's fine and sometimes it's not.

1) We had chars that knew each other in-game that pvped together, which was a no-no. They're gone, moving on...
2) It was stated by Nep that as long as you don't pvp together and didn't "abuse" it, it was fine considering he grouped with his wife a lot and they have had characters at the same time several times.
3) So we made chars that never pvped together, didn't even rank together really, and purely hung out to enjoy Hell together.
4) With no warning we were denied on solid characters purely for the Hell trip when we did exactly was stated by Nep as "fine" by the rules around no-pvp together.
5) I've never seen anyone denied for OOC hell groups which have existed from the beginning of CF.

So yeah, I think the rules should be clearly defined. Maybe if it was clear about what your problem is with OOC knowledge of others I wouldn't lose 300 hours on a Scarab character because of it.