I have noticed that couple of times, in particular with LA Times Twitter account. Some images posted there contain horizontal black line, approximately 1px wide. It is not my screen being funky. I have asked LATimes, but got no reply, and googling didn't help.
Is there practical reason to have that line or is that an artifact of some processing?
In both examples images are credited to AP (Associated Press). Also, of course, not all images in that twitter have such lines.