Thanks Mike.
I'm unable to fully test this for the user since my interface as admin editing their profile is different from what they see. For example, I have it set to one URL and when I'm editing it as Admin I don't get any errors or anything. What will be the behavior for me as admin if I enter 2 links and only one is allowed for the usergroup they are in?
Some additional background: This user's signature was converted over from another platform and they haven't logged in since, which is how 2 URLs got in there. When I go in to edit it, I don't get the same behavior that the user would.