My device = Kingzone K1 turbo
I exspected that the comparator' back is shining AND the comparator makes a redstone signal.
I saw the comparator was not activated, even it did not make a redstone-signal, normally the comparator should do this!
How to reproduce:
1. Place a comparator
2. Place a detector rail as a redstone-power-source at his back
3. Place any type of minecart on it
4. You will see, the comparator is not making anything
UPDATE: As of 0.16.1, this bug is only partially fixed: Comparators can receive power from redstone dust that is powered by a detector rail, but they cannot recieve power directly from the detector rail. Sometimes, however, placing a comparator next to a detector rail will cause it to be momentarily powered when it is first placed, giving off a pulse of at least 1.5 rticks (3 gameticks), or however long a pulse is required to be in order to invert a redstone torch in MCPE. See this video for a demonstration: youtu.be/9E4gOTQ4W7c