1-tick (redstone) pulses, when activating comparators in a line, visually power them, but actually don't since the last comparator in the line doesn't turn on or power anything. It also doesn't activate the power in the side, when using it in comparison or subtraction mode.
Since a comparator has the same delay as a 1-tick repeater, and since other things such as repeaters and pistons get powered, this is unexpected. Even if it shouldn't power a comparator this way, the visual powering is still a bug.

To reproduce

1. Place an observer with a line of comparators in front of it.
2. Activate the observer.