Whenever you copy and paste text from anything not from xat (with the exception of a regname from the user card) an additional space is added than one you included yourself.
Ive noticed this while assisting clients on ARC, using their regname to find their ARCbots account username. This issue has been ongoing since the creation of HTML5, never thought anything of it, but think it should now be looked into.
Copy their username (or any text not originating on xat)
paste into the chatroom
click enter to post the message