Interesting conversation.  This thing about breathing in through the nose is actually very subtle.  The main reason to breathe through the nose as opposed to the mouth, is for greater breathe control.  Whether you breathe out through your mouth or your nose varies between traditions and practices (most martial arts breathe out through the mouth but many yogic practices (Ayengar being an example) breathe in and out through the nose.  At any rate when we talk about breathing through the nose we’re not talking about simply breathing through the nostrils.  What do I mean?  Stand in front of a mirror and breathe through your nose deeply.  Unless you have practiced this you will probably notice that your nostrils flair just slightly with each in-breath.  That’s nostril breathing which isn’t quite what we’re after.  Now try breathing in through your nose again but this time as though you were just slightly snoring (there should be absolutely no flairing of your nostrils.).  So the focus is at the back of your nose.  You should be able to hear yourself as though you were quietly snoring.  Notice how much more control you now have in the amount of air you can draw, how effectively it reaches your lungs (which feels like your belly – i.e., it expands with each inspiration) and the control you have as to the speed with which you draw it in.

Credentials (for MT’s benefit):
25 years practicing Chito Ryu Karate (until my hips gave out)
40 years as a meditator
PhD in Consciousness Studies (which includes investigating the nature of deep meditative experience.)