In a last week or so, I noticed at least two people wearing their helmets backwards. No, not on Divvies or rented bikes. One was a man, one—a woman. Judging by their clothing, not new to riding.
Don't think I've ever seen anything like that in real life, though there are quite a few photos on the net.
Is it a new fashion trend I should know about?
Not a fashion trend. Some people just don't know. I saw a lady wearing backwards helmet also earlier this week.
Wear this - on your bike!