If you get the InventoryClickEvent and check if it is a trading-inventory, you can get the ItemStacks by accesing the diffrent Slot-Ids.
Try using this caracter: "»" If that isn't working, can it be that your using a texture pack of some kind? Are you using...
The most popular Faction-Servers use 1.8.x I really would not go lower than 1.8, because nobody uses that version (<=1.7.9) anymore.
If you are using normal YAML-Configuration, you should be able to just set the value of "[uuid].reg-perm" to a value and the section should be...
Maybe you can try opening the world in mcEdit or something like that and then reexporting it. I am guessing that the world file is corrupted....
Separate names with a comma.