Selection highlighting is very slow/laggy in markdown mode
When composing in markdown mode, if I try to select text with the mouse (push left button at the beginning of the selection, then move mouse till the end), I have to wait 2 or three seconds at the end of selection without moving my mouse and without releasing button before the selection highlighting gets updated. If I keep the button pushed and keep moving my mouse around, selection highlight update gets slower and slower (have to wait 5 or 6 seconds after stopping movement to get selection highlight updated). Maybe this is not easy to notice on a fast PC. But selection in html mode and in text mode does not have this behaviour on my machine.