Interesting topic though I don't have the issue. Searching the NHTSA DB, lots of complaints for different brands including Mazda (but none on M2). I see TSBs on many various brands/models but that does NOT imply it's covered under warranty or free. I also see it varies by dealer whether it's a warranty item or not across the board.
So it's a roll of the dice. If you have opened up the lights or modified them, I'm sure they'll smile and say not covered. Personal opinion, it should be covered but that doesn't count. I'd ask them to pull a lens from stock and show me where the vent exists. It could be a faulty gasket/seal and if an obvious vent does not exist then you have a case. I'm not sure why the M2 lights would have a vent. This is one of the lowest light cars I've owned. I commute from the country (animal hazards in the dark) and I could swear the lows on my 02 Miata are 2 or 3 times brighter than the highs on the M2. So I'm not sure why a vent is needed on the M2 because it's not due to bulb heat from the extremely bright lenses.
Let us know how it turns out. I'd prefer to seal my lenses if a vent exists. I would at least log a complaint on the NHTSA website stating it's a safety hazard (1) condensation reduces visibility and (2) it could blow the bulb. I see they have a TSB on several models including the 2012 M5 for condensation per NHTSA.
