Add the possibility to distinguish different accounts of the same user on the UI

I also believe that using a configurable display (using some cached velocity script) is the most flexible way.

Will this configurable display generate HTML?

• Yes: can we expect that the provided HTML works well in all the places where users names are displayed?
• No: isn't there any use case where we (XWiki) want to style differently the user alias or whatever user property is used as qualifier? Or maybe we need to display it on a separate line. Or maybe that qualifier is already displayed in some places where the username is displayed, which would lead to duplication.