Thanks all for your help. It's quite telling that even on FT there's no consensus on AF's checked luggage rules. To make this even more confusing, I can only repeat what I already hinted at earlier, namely that on another HOP flight with a Mini ticket I didn't have to pay anything upon check-in (the way it should be IMO). I had purchased a 1 bag luggage allowance online for 30 euros and combined with my Flying Blue Gold status this was sufficient to check 2 pieces of luggage.
By the way, how do you pay for a second piece of luggage if the first one is free (due to elite status)?
As far as I remember, there's only one drop down menu on the AF site that lets you buy either 1 or 2 (or more) checked pieces of luggage, but you can't select if the piece you're paying for is the first or the second.