It has nothing to do with UOAssist. It's the "Item Properties" icon
Log into each character, go into Options on the paperdoll, click on the "Interface" tab (looks like a computer mouse).
Scroll down until you get to "Display Item Properties Icon" (it's right above "Object Handles")
Uncheck "Display Item Properties Icon", click apply, and close the Options menu.
You'll have to do this for every character.