In imagemaps it isn't necessary to make a colon in front of the project to avoid the interwiki navigation list, if you want to link elsewhere. So you can link to the Commons main page from the english wikipedia with [[commons:Main page]] in an image map and it will link like [[:commons:Main page]] in normal text. That's okay, but another part of the parser seems to be confused by that. Special:Whatlinkshere/Main_Page on the english wikipedia will then list the page for linking to it, but of course it doesn't link to the en.wikipedia main page but to the commons main page.
Version: unspecified
Severity: minor