[dr4g0n]

> The so-called “ow zone” is a zone that is hard to reach with your thumb, like corners of the screen.

The image that goes along with this point demonstrates the areas that are hard to reach for right-handed users, ignoring that ~10% of people are left-handed and have trouble reaching the opposite corners. Your design shouldn't assume that two particular corners are bad and the other two are fine, all four corners should be used for uncommon options only.

[ovulator]

I’m right handed, but I use my phone with my left hand. Most of the time because I need my dominant hand to do something more complex. I don’t know if “handiness” really determines the hand in which you hold your phone.

[Ambadassor]

I'd like to stress that this is the correct solution. It is not enough to just slap on a "left-handed mode" that mirrors the UI. Most left-handed people don't use just their left hand when operating their phones - they use both, but prefer their left.

[toportyan]

You are correct. Let me point this out in an update.