We discussed this among staff a few weeks ago. At this point we’ve decided it might be something to work on in a few years but it’s not a priority and some real limitations (eg no more than 10 users per group or something) would need to be included, which might curtail its use as a way to promote projects.
I think personally I’m not for it, although I understand its use cases. But I don’t think iNat should be a messaging platform, and if a large discussion needs to be had, I think it’s best to have it publicly on an observation or flag (@megachile does point out the problem with that approach, though).