Desync when?

I'm doing some multiboard stuff, and I need my multiboards to display different info to different players. The problem is there is no 'show for player' option in the multiboard legenda. Now I use the 'local player' function brought into GUI by weu to create another multiboard for each player. This should work fine except that I'm afraid of desync errors, since there is another multiboard with the same name though on each players' computer.
When do I get desync errors is it only when things within the game world are not the same or also when global vars aren't? And what about locals not being the same?
TNX in advance

Using Local Player is a good way to cause desyncs, in my experience.