the first time I installed a vintage blade front sight onto a Winchester lever action I fit it in backwards, but thats a little less obvious than the rear sight, lol
I would think along the same lines as Baboon if the gun has evidence of ever having had a scope mounted and has a non-fold down rear sight. The rear sight often can be in the way of the scope's bell at the front and many would remove the sight, store it and possibly lose it or not be able to find it again. A simple solution, so you do not separate the sight from gun, turn it around. Thus it would likely sit out in front of the scope. Of course, if it is a fold down sight, why bother with changing it.