I wasn't even aware of their existence. For simplicity's sake nowadays I just tune out whenever a sentence contains the word IEM but not FitEar.
But with Rin I'm never sure whether he's being bitingly sarcastic or not. When he writes it comes through for me as if he's just being sarcastic all the time in order to create that sense of impartiality. Or maybe it's just me. Probably just me.