Feathery’s editor in mobile view is 480px wide, whereas most mobile devices are 360, 375, or 414px wide.
So you’re likely experiencing this issue because you’re designing for 480px viewport, but your device’s screen width is smaller. I made the same exact mistake when I first started using feathery.
I’d recommend decreasing your mobile font size and keep testing on a mobile device until you get the perfect layout. The overlapping text issue might be caused by your line spacing setting.
I do hope the feathery editor will eventually allow us to set a custom editor preview width and add a third breakpoint for tablet devices…