If what I think you're saying is correct, then yes, I agree. I feel that the ability to highlight lines would be awesome (e.g. set a marker on that line, potentially a pink/red background, or even more preferably the ability to select the color).
Even when I'm working on files that are subject to syntax highlighting, a lot of them are absolutely gigantic (don't go off on me about "you should make them smaller," I'm working on someone else's code). Sometimes the code is so mixed up that it's hard to find specific functions. It'd be nice to highlight a line so that a quick scroll through the file would point those lines out to me.
Customer support service by UserEcho