This is a great idea, a subtle mix of the gradients and some readers' select-a-few-lines-at-a-time habit.
Or, to mix in another idea (from philip1209) downthread: have the hover-effect add color-matched dots (or other glyphs) at the corresponding line-ends, currently under the pointer.
Or, to mix in another idea (from philip1209) downthread: have the hover-effect add color-matched dots (or other glyphs) at the corresponding line-ends, currently under the pointer.