This is on Mavericks with the 25239 build. As I type, or when lines soft-wrap, I get these strange gray lines drawing through my text. Sometimes through a line, other times between two lines. Seems random. They go away the minute I scroll the editor.
What magnification are you using? 
150%
Lines are often an artefact of using magnification, particularly percentages that don’t scale well within the pixel metrics. My guess is that is what’s happening, but 150% ought to be safe. I’d better leave someone better informed than me to take it up, but I’d be trying at other scaling factors to see if they go away.
damon,
I get these odd lines too, also at 150% magnification. The issue, xiamenese, is that I didn’t get these lines before. That said, it’s so minor, I wouldn’t have reported it.
@Benjamine: Oh, it’s not ruining my day or anything, but if no one reports it, it never gets looked at. It’s not a high priority, but I figured (after looking through ChangeLogs) that no one was aware of it, so I thought I’d mention it.
Are you in page view, too? The problem is that the OS X text system has certain rounding issues when magnified to a non-100% value, so that you get slight pixel breaks in some areas that reveal the background through them. They usually depend on a combination of screen and magnification. They’ve been an issue throughout Scrivener’s history, and I’ve done a lot of work over the years to reduce them as much as possible, but it’s seems impossible to get rid of them entirely, unfortunately. Also, it seems that Mavericks has introduced a lot of flakiness in all sorts of areas. I see text “wobbling” and distorting even at 100% in normal (non-page layout) mode, which I know is nothing that Scrivener is doing and is down to bugs introduced to Apple’s underlying text system in Mavericks, so I’m not surprised that these issues are also causing line artefacts when there is magnification. It’s hugely frustrating, but I’m hoping that Apple will address these things with updates to Mavericks (actually, I wish they’d spent another six months tidying up Mavericks before releasing it, but hey…).
All the best,
Keith
I figured it was a Mac drawing problem. It only showed up for the first time when I upgraded to Mavericks, so I had my suspicions. Just wanted to report it in case no one else had. Now that I know it’s an ongoing problem, I’ll just work with it.