GetLocalPlayer desyncs whenever it is about to create a handle (most of them, as they now are called agents which extends handles). All types which are referencecounted in wc3, thus if something is created locally, it would never work because the packets between the computers and the server would have mismatches. But for instance, a string or integer or real or something like that can have their local value, as long as it doesnt involve creating something which results in differences. Eg, you can not hide a unit, because that would make a unit available on the map for one player while it wouldnt be for someone else. So basically, one would be allowed to attack while the other believes it doesnt can move at all and is gone. Thats an example of a desync.
Multiboards and leaderboards are things which doesnt desync. Or well rather, setting a value on a board locally would, as it is in multiboard, actually setting a 'multiboarditem' value. But nothing will never happend if you only show the leaderboards locally. That is pretty much what happends when a team player leaves a ladder game: A multiboard is created but only showed for the team.
