An interesting question, my 2c coming from a developer but UX lead and also having designed interfaces with several internal scrollable areas.
A few points:
Visible scrollbars should exist if the content is large enough to require a scroll, as the presence of a scrollbar signifies and affords that the content can be scrolled.
Infinite scroll is my ...
I'm so glad, somebody raises that question. It's Microsoft's fault that you have to write such a long question, because they created that inconsistent mess.
Everything started with Microsoft making cross platform + touch input the top priority for Windows 8 and future Windows releases. That brang us
a Windows experience that was consistent with Windows ...