When writing a longer answer, the otherwise, very neat preview becomes tedious. I have to scroll around a lot. In another question making the preview scrollable was suggested.
My suggestion is a different one:
Show first only an area around the last edit as a preview. Some 20 lines, or so. Only then, show the complete preview.
Scrollable areas are particularly confusing on mobile devices: You have there the simple page-scroll which works very intuitively. But a further scrolling within the page is very confusing.