@dansup I would lobby for this to be a view option so the user can choose whether they prefer the square density and balance, or to see the photo as the poster intended. (And I'd lobby for the default to be to follow the poster's intent.)
I usually crop my photos to square before posting, as I've felt that tends to match this context better. But sometimes I've felt it's important for a photo to be a different form; having the app make its own decision means I might as well not post it.