If you enter too many characters into the reason-textbox it just displays "R" as reason. I know it's not really serious but it's a bug nevertheless. So maybe u could limit the numbers of chars one is able to enter as reason...
It works fine with 20 chars but 30 already results in "R", so the magic number is somewhere in between (i'm too lazy to test them all at the moment :D)

one thing i dont understand is why do u need a reason to change map?

You must have a reason, or did you just randomly click on Vote Map ? :p