User blog comment:Lorchyism23/Joining the Thalmor/@comment-209.33.94.100-20130324004049/@comment-1840877-20130401195146

But what about the lore? As was mentioned below, the Thalmor are supposed to be your enemy during the main quest -- ergo, they are canonically your enemy. Joining and assisting a faction that you're supposed to be enemies with makes no sense.