I am uncertain whether this is a bug or not, but whenever you activate a command block via redstone more specifically with a pulse such as a redstone button, and have a comparator on the other side, the comparator will output a signal (when the command is executed successfully) though the comparator will stay giving off a redstone signal, this happened while using a chain, and impulse command block, I am not sure whether this is an intentional feature, if it isn't I would love to see this fixed due to it impeding my progress on a command block chain i'm working on.