Hi Ralph,
For what it's worth, the Username field that appears when posting is not really a login, but for guest posting (since we don't require registration to use our forums).
It doesn't allow fewer than 3 character usernames for guest posts, but had it accepted it, you'd get an error message saying "The username you entered is already in use, please select an alternative" because it won't let a guest post with a username that already exists in our forum (which would be the case for your username).
Due to the latter error I don't think it's much of a bug.
If you happen to notice the Username field when you go to post, be sure to log in before posting.
Also, if you log in using the username and password fields at the bottom of the forum, there's a checkbox "Remember Me" that will keep you logged in longer saving you from having to log in every time if you visit the forums frequently.