It's another one of those, "can bikes ride on the sidewalk" gray area issues.
Cars and scooters alike all have their designated parking spots and so do bikes! Technically speaking, bikes should be parked in designated parking spots. However, since there's no license plate on a bike and no way to track who owns the bike, I don't see anyone actually following those rules.
Bike parking in Taipei is scarce and unless you know where they are, you won't be wasting time on an oBike to find one since you're paying for that extra time!