When I was waiting in priority check-in in YVR, I was questioned whether or not I was flying business class like I didn't know where I was. I think it had to do with the fact that I look young. In the business class cabin, I had great experiences. The SD came and had a 5-10 minute chat before takeoff and treated me like any other passenger when serving my meal.

Interestingly, I have never been asked for ID when ordering alcohol in business class but I have when in economy. I have even asked the flight attendant in business class what the drinking age was on a flight from the US and was told "don't ask, don't tell." However, on a flight from Athens, I was asked for ID and the SD insisted that the drinking age was 21 in Canada. I was under 21 at the time so he didn't want to serve me. I told him that the drinking age was 18 in Quebec (where we were landing). I got a 15% discount code out of that.

I personally think that on the ground, if you look young they must assume you are flying economy before they can see your ticket. I doubt that had I been in a suit that I would have been treated any differently. It is likely a case of judging based on appearance. I look young so therefore I must not have the money to fly business class. In my experience, I would argue that there is a clear distinction between business class and economy treatment of younger people.