someone said that selling and buying on the same account ( horde->alliance ) was illegal while selling horde->alliance on two seperate accounts was fine.
Does anyone know if this is true? if it is true we should let everyone know the proper rules.

I have sold stuff accoss accounts. It's usually something collected or made like herbs, ore or bags and I sell them cheap like 1c and buy them back on the opposite account.
I have both accounts open at the same time auction & buy in like 10 seconds. I figure if someone out buys me in that 10 seconds then they deserve to have it... it's never happened though.
I've never tried to move much in the way of gold because I usually find my mboxing teams have no problem making their own gold. I just move enough gold to seed my character ( like 100G ) which you can do with selling some linen cloth for 100G each.