I haven't insert an input type="text" coz you have to be sure of the user's login
I thought it could be better to choose directly in a list and I wanted to "play a little" to show or not the user in the list if he had or not already been added
But you are perhaps right
That's why I consider it as a Beta
For the usergroup, I agree Blaine, but I created it for a forum where, in only one forum, only one member is allowed to create threads, and I thought it could be a good idea to do a hack for this, it may help some users here
And it's longer to create an usergroup, to change a user's usergroup than to install and use this plugin