If the pointer is dragged by a user or moving due to a click on the slider line, it is detached from the connection line to the diff column. This can look awkward (comment: "like a detached head").
Suggestion is to lower the opacity of the lines to 30% if the pointer is moving due to a click or is being dragged. So you start dragging, the line fades a bit, you stop dragging, the line regains opacity.
↑this is how it would look like during drag (reduced opacity)