I realize this was an old topic, but for all those who find it these days...
The 2013 Nexus 7 DOES INDEED support the 4-pole stereo headphone/microphone standard used by all modern Android devices.
I verified it to be certain using my "Beats" mobile phone headset that came with my HTC One, and I get Stereo Audio, and the headset microphone over-rides the N7's internal microphones.
Also... the pushbutton on the headphone cord also works... in music player it's a Pause, other apps may use it differently.