Users in domain-based subwikis do not see links to global users correctly

Steps to reproduce:

• set up a wiki with domain based subwiki, and forums app on the subwiki
• as main Admin, create a forum in the subwikis (so the Admin from the main wiki is the "creator")
• create a local user in the subwiki and log in as that user.

The creator of the forum should be shown as "Admin". What is shown instead is "$creatorDoc.name".
Click on the forum name, and the forum overview contains (slightly different) garbled content where the admin should be shown.

This is only a problem when the sub wiki is domain based (xwiki.virtual.usepath=0 in xwiki.cfg). No Problem for path based sub wikis.