Offtopic:
Regarding your Ask HN thread - some years ago I used (well, tried to) a small smartphone stylus which 'docked' in the headphone socket so it would be always with the phone. It wasn't good for me, because it wasn't sensitive enough for sketching, but overall it was fine for navigating the UI.
If your phone has no 3.5 jack but you use a case it can be attached to the case.
Maybe you can try to use a notebook style case, so your palms would sweat the case, not the phone and therefore you would have a bit less trouble with false touches.
Eg: https://www.amazon.com/x-girl-P-TPS-XG1-Collaboration-Stylus...