oh, sorry about that. I wasn't getting notifications for a bit. Unfortunately I can't disable it in the shoutbox. You can turn up the time it takes for the hover to appear. 3-4 seconds would be good, so the link will only pop up if someone really wants to view it. Once it has been looked up though it's cached and will show up immediately for that user. I'm going to come out with a version soon so you can disable it on the forumhome.
I cant remove it just from shoutbox though because of how the formatted username is set.