The user base is exactly what's not easily replicable.

And trying to "migrate" a user base from Instagram seems like a shot in the foot in this context, even if the whole mechanic of the platform is pretty much the same as twitter, the user base is already completely different

Having that community and culture is the moat. Even like things like “ratio” and “subtweeting” are part of the moat if you’re trying to create a clone.

However, that doesn’t mean there can’t be a next big thing out of nowhere like TikTok.