>>81192483Is it? I've been wondering about it since I've noticed Suityan using it quite a bit, to the point that I've seen at least one (presumably male) fan complain about it due to how wrong it feels even when she's using it as a joke. That said, 俺 used to be the gender-netural catch-all pronoun before being supplanted by 私, and survives as such in several rural dialects although usually with a funky dialectal pronunciation (oira etc.). Suisei has being from the sticks as part of her character lore, so that could potentially explain it.
Also it's been my impression that 僕 is the one used by tomboys in anime probably thanks to it being traditionally accepted as a female pronoun in poetry out of metrical considerations. But also that the only people to use it in real life are feminist activists and even then those tending towards lesbianism. And I've no idea whether they use it only as part of their public persona as an activist or whether they also use it in private.