You can PM any Global Moderator to do so.
You can also PM any appropriate 'Sectional' moderator to do so.
For example, if you would like to change of a thread in the market place, you could contact a 'Market Mod' or a 'Global Mod'.
If however you would like to change a threads title in the Off Topic section, you could contact an 'Off Topic Mod' or a 'Global Mod'.
sythe.org/showgroups.php - Heres a link.
Hope this helped; also be sure to PM a mod that is online.