The player's own name (
UnitNameOwn) if enabled, gets hidden in combat / by the Personal Resource Display (nameplate for self)
It would be nice if this didn't happen for your own name, aside from nameplate for other players/npcs
http://us.battle.net/forums/en/wow/topic/20745036181 Personal Resource Display hides my name.
http://eu.battle.net/forums/en/wow/topic/17613401892 Hidden name in combat