The diamond-shaped icons that denote friendly team member class and distance are "always on top." Thus, when an enemy is between you and your teammate, your teammate's identification icon is superimposed over the enemy. I've been shot plenty of times because I reacted to the friendly icon and not to the character model behind it. While the friendly icon is helpful most of the time, it would be much less frustrating if enemy character models were "always on top" so they obscure the icon of any friendly teammates directly behind them.
Friendly identification icons get you killed