Actually, there are specific rules for each group-style RP subforum (Open RP, Group RP, Persistent & Shared Worlds RP). And, for each one there are designated sections for interest/coordination, profiles and anything that's OOC for a particular RP. For Persistent & Shared Worlds, however, there's an additional section for world profiles. Anyhow, for each group-style RP, you MUST have a profile for your character. If you don't, you are risking your RP. Meaning, it could get closed down if you fail to comply.
Basically, the rule of thumb. If the RP has more than 2 people in it, make a profile and place it where it belongs.