I was thinking that the highlight command should get a bit of tweaking or fixing.
So after when you type /highlight <name> <seconds> you would have to type /reveal to undo the highlighted blocks pretty much forcing you to rejoin the server to see the block that was actually placed there instead of the highlighted block colour. What could possibly happen is that after the amount of seconds that you entered it will automatically reveal by itself without forcing you to type /reveal and rejoin the server.