Originally Posted by Maiden33
Honestly I have never actually read an explanation as to why double headliners can't exist on this site.
Well, for starters you could check out the sticky thread at the top of the page titled "How To Post A Set List & Title Guidelines
And for a little more info you can check out this post, which is just the most recent post concerning the title format and the database indexing. Link
Edit: I just added the above explanation to the "How To Post A Set List & Title Guidelines" thread for future reference.