You should never count on the fact that the same username on different platforms means the same user; don't assume anything if you want to avoid (bad) surprises.
To me, that's common sense and I don't see how anyone would just assume, without verifying, that the same username is associated with the same person cross-platform--especially if there's a business deal involved. There was someone impersonating me on telegram a while back, which prompted me to add a message on my bitcointalk profile and I know mine was definitely not the first case of that happening. I think it's a common scam tactic in general, and it seems to happen with bitcointalk members quite a bit. Glad no one got burned in this case, and props to OP for warning the community.
