It would be great to at least have an option for swiping left-to-right to work as the "back" button, even in menus.

Currently it only seems to work if you've got a post open. If you for example swipe left-to-right when viewing a community, the left side drawer menu with your subscriptions opens instead.

I personally find the back button a little hard to reach with my right thumb, and having the swipe to go back be consistent helps using the phone one handed.