That's actually the bottom edge of the fretboard. When they masked and then scraped the paint off the edge of the board they just didn't go down far enough. I've seen it many times on Gibsons with and without binding. If a guitar dries out the wood contracts due to a lack of moisture thus making the line a bit more visible since it gets sucked in and on clear coated glossy guitar (unlike your thin satin finish) it can crack the paint in that area and around the nut, also very common due to owners letting guitars dry out in winter months.