Blinking tasklist and window menu buttons remain highlighted when urgency hint is removed externally
I believe this is another regression from 4.14 to 4.16, caused by commit 0ede27ae, which was part of !10 (merged). I think it's reasonable that one might not normally notice this happening, because in order to make an urgent hint go away, you normally focus the window that has set this hint, because it is trying to tell you something important that you should pay attention to.
Unless you have an application that sets the urgency hint for literally no reason, like Discord. It seems to have a pretty stupid attitude. "I have started up! Pay attention to me!" And with the help of devilspie2 and wmctrl, I say "shut up." The urgency hint is removed externally, which means I never have to focus the window, which means I never have to click the tasklist button for it.
This issue also crops up if you have both window buttons and the window menu. I do have both because I make extensive use of workspaces, and it's nice to have a way to view every window on every workspace. So if you use one method to focus an urgent window, the other one won't get disengaged.