Steps to reproduce:
- Login with Admin
- Create 2 global users: U1 & U2
- Create a new subwiki and in step 2 set U1 as the owner and U2 as a member
- Use DW to install the UI
- You'll get a merge conflict for XWiki.XWikiAllGroup: choose "Keep the current version"
- Hover over Home and click "Wiki Index"
- Click "edit" for the new subwiki
- Click Edit
- Change the subwiki's owner to U2
- Login with U2
- Hover over Wiki; you won't see the Administer Wiki link
- Login with U1 (the previous owner); you'll have both Administrative rights and the right to delete the wiki
Basically the previous owner (U1) has more rights than the current one. I think U1 shouldn't have any administrative right once he's no longer the owner.