Circle around tags
Tags are a Revit Family in their own right.
Select the Tag in question.
You will now see the "Edit Family" button on the Ribbon- go ahead and hit this
The "Family Editor" will open with the Tage displayed, ready for editing.
The Elipse is simply a 2D line around the Label. Go ahead and delete the Elipse
SAVE the new version of the family.
Load this new Family back into your Project using the button on the right hand side of the Ribbon
Hope this helps