Sometimes, when playing ARMA Reforger multiplayer games, friendly name tags do not show or display. This sounds like a similar bug within ARMA 3, and very likely still persistent today, possibly due to network de-synchronization.
With the player versus player scenario, players stealing uniforms; this bug is now becoming extremely frustrating, especially after shooting/killing one of your own, due to increased paranoia and increased anxiety. All because the player was new to the game, did not know how to communicate with a radio for confirming his presence as friendly, standing up-right within a base being taken, with no name tag showing and wearing a friendly uniform.
Just a few hours prior to this particular scenario, I witnessed two players at the simulated 3D ~300 feet away, one had a name tag, the other player did not. Finally after both players running towards myself, the second player's name tag finally displayed, while running apparently side-by-side.