A request for evidence -- particularly from Isobel, who is well-armed for any battle of wits and sources -- is not a claim that someone is doing it wrong.
With the PF we've got, though, we've established that individual Matari (who are living as Matari) can't just choose to take tattoos, and you have to squint fairly hard at the statement about the Thukker to read it as saying that there are Thukker communities which embrace tattooing and will therefore be in a position to give members the appropriate approval to get inked.
And yet Isobel has said:
I assume what kind of tattooing traditions remain for each Thukker caravan, clan or family would be fairly variable - some would not tattoo at all, and others almost as much as their cousins in other tribes.
This seems to go against the statement that "These people have rejected many of the strongest traditions of the Minmatars, such as the tattooing process."
I'm curious about whether Isobel has another source which supports Thukker tattooing (she's often a good source for such things), whether she's reading the statement about rejecting the tattooing process differently to me (which I've said above is possible, although I myself wouldn't build too much on that reading without a clarification by CCP of a paragraph that's not very clearly worded and seems to go the other way), or whether there's some other reason for taking input which says -- most likely -- that Thukker don't tattoo and coming up with output which says that there would be a range from "not at all" to "almost as much as their cousins in other tribes".
Of course there will probably be people from Thukker backgrounds with tattoos. Some will likely live in the Federation where people will defend their right to take any ink they fancy. Some will have been adopted across tribes (PF suggests that's a last resort but says it's possible). Some will have (scandalously!) unauthorised tattoos but will mix in parts of Minmatar society where no one knows to call them on them. Some might work with Angels or other groups outside Matari ways, where ink might have quite different meanings.
But if I meet someone who claims to be Thukker, living as a Matari, and bearing tattoos, at the moment that's going to have me wondering what's going on there.
That has the potential to go anywhere from a really interesting personal story to "they're delusional" or "they're trying to pass as something they're not".
And if I write about Mata's time visiting Thukker caravans to learn about their dances, I can mention how strange it is to be among unmarked Matari who are still Matari, and maybe how people flirted with her differently or not at all because it was immediately obvious from her marks that she was an outsider there. I like that sort of thing, but it doesn't work so well when everyone can do anything. There's a lot that we can plausibly say is open to anyone: why apply that also to the things where the evidence suggests otherwise, thus blurring some really interesting distinctions?