I think I did it with memory editing too... Just make your name something very distinct and then search for it at the server selection screen and change it. I think that works unless they patched it, doubtful, they seem to have almost no anti-cheat staff...
Have a buddy verify it. more than likely your changing your name in the clients memory. Others may still see your name, while it has been changed to you.
want a good example of this, change the value of a money address in a mmorpg. same thing.
two things you need to know the difference between, server side and client side variables.
i haven't even installed any arma. but i could tell you that when you join a server it sends information about yourself to the server, such as name, rank, stats, unlocked guns w/e however the game works.
your method is trying to take the name out of the server once you joined, where you should be looking to keep your name out of the server altogether.
good luck.