I mean this in regards to players who might claim to have something that's 'official' but owned by someone else. Like, some new player who claims to have a certain item or bijuu. Personally, to facilitate RP, I just play with them as if they have it. From my experience, they most likely won't hang around for too long anyway. So I'm more concerned about making their stay as fun as I can. So what do you guys do?
If they have a big ticket item (Edo, biju, hiraishin, etc.) then there is no point letting them RP the canon stuff because when they get into the bigger fish tank they are just going to get shot down, politely or not. If they have more minor stuff that someone else technically has claimed but is not really around for (dragons, one of the more obscure 7 Greatswords, spirits in a gourd, etc.) then I am more willing to work with those.
Rani is not new and he is not technically on the dragon scroll, but I am perfectly fine with him summoning and having his dragon Karie, cause even before I got on the dragon scroll I was flying around on my private contract dragon Rita. I personally went through the testing process of signing the main scroll with Rares more as a formality, and to later start using more dragons as my character progressed; Rares probably saw it as me making myself an "official" dragon summoner to be recognized as I started to grow towards that Jounin-Sannin level of RPing.
Now had I started summoning dragon kings before signing the main dragon scroll, I imagine Rares would have had a very different attitude towards me and shut me down much sooner.
Especially towards personal companions, if you have been RPing with it long enough and it is integral enough to your character, I really don't care whether you're on the official list or not; I've been there, I'll RP with you and your companion.
Fight RPs though, are slightly different, as how much is at stake is what determines how much of a stickler I am for the wobbly and narrow.