User Control is where you can set nicknames that you do not wish to see text from in the partyline or gameline. After pressing the Misc. Settings button at the bottom of the program, simply left click on the words User Control on the left side of the program, as seen here:
Having done that, you should see something like the following:
Simply add the nicknames to the large edit box (one name per line) that you wish to ignore. Alternatively, you can right-click on the user's name in the partyline userlist box, and choose Control->Ignore User, which will add their name automatically to this list.