search eliminates most of the upenn.edu hits, and it appears there are a number of publications that use UPenn.  It's also clear the University wants to use Penn, not UPenn.  So, some language suggestions: "...; UPenn is a widely used but unofficial nickname"?  or perhaps "... (also known as Penn and UPenn, though Penn is generally preferred by the University and people associated with it)"?  I think we have enough here to craft language that makes it clear the University intentionally and systematically uses "Penn" for all of its official documents and media, but that UPenn is also in wide use (assuming people agree that's an accurate assessment of the facts?).