A repeating command block that requires redstone will still output an active signal after being turned off. By right clicking on the command block to see the command and clicking "Done," the signal will switch off. In addition, the signal will not switch off if you click "Cancel"
My opinion: either the signal should remain on (due to the final command being successful) or off (due to the command block being powered off) and not dependent on the player looking at the command and clicking "Done"

How to Recreate:
1) set down a repeating command block that requires redstone
2) write a command in it that will always be successful (ex: testfor @e)
3) set a comparator coming out of the command block
4) power the command block; note the comparator turning on
5) unpower the command block; the comparator remains on
6) enter the command editing GUI and either select "Done" (comparator turns off) or "Cancel" (comparator remains on)