I tend to RP the WoL as a nebulous, agendered and non-racial being just to keep things fluid between RP encounters. Better if they never come up, but if they do I'm comfortable using the most basic and non-identity confirming details just to keep things easier across the board. About my only rule is that if my characters meet someone actually claiming to be THE WoL they're going to laugh themselves into a stupor and I'll likely immediately cut the scene. I don't have many rules with my RP but I don't enjoy RPing with people who play as either NPCs or as the big, bad hero of the whole story. It breaks my immersion five ways to Tuesday.
Nothing against NPC roleplayers, but I've been to one too many RP events where one has absolutely gone off the deep end and ruined the experience. Such as Nanamo showing up to an RP fight club and then proceed to try and order everyone around and tried to take over the event. It sadly was not a troll.
Beyond that I feel people can RP whatever they want, so long as they accept that not everyone will agree or want to RP back if it breaks their definition of the lore.