Every reply gets its own elbow
Replies used to hang off the reply above them, so threads read as a chain. Now each one turns off its parent's column, and the dashes run straight through.
Open a commit with three replies and look at the graph. Each reply leaves the same vertical line on its own rounded elbow, one after another, instead of dangling from the reply above. The dot for the replies still hidden sits on that line, and the dashes carry down through every turn.
Credit goes to jubianchi, who taught every reply to branch off its parent. The column is 2 pixels wide, its dashes 4 pixels with 4-pixel gaps, and each elbow turns with a 12-pixel radius from exactly where the one above turned, so the rhythm never restarts. Reply to the last commit in a thread and your card fades in over 300 milliseconds while the line draws down to meet it.
One catch. The column stops three levels in. Nest replies deeper than that and the thread flattens back to the left margin. There is no elbow and no column, and the show-more dot leaves the line.