@karl This is your server, which succeeds or fails to "auto link" a user, not AndStatus. And this is why mentioning a user in AndStatus by WebfingerId is more reliable. More on this: https://github.com/andstatus/andstatus/issues/312
Qvitter works differently, because it has direct access to the server-side database AFAIK. It's a pity that Qvitter does some smart/productivity things for itself only, not for all GNU Social clients, which access the Server via API remotely...