If it can register user with hyphen as "user-name" you can not look to their profile. As is always "wrong uid". Is this a bug? For if not to a prior registration is not possible.

No it is not a bug. For some necessary reasons, Jcow forced members to use "0-9a-z" as username characters. But we will think about the possibility of allowing "-" or "_" in username.
Thanks for advice.