Inactive redstone torches disconnect nearby redstone wire as if they were opaque, while affected wire looks visually connected.

Steps to reproduce:

1. Build a structure shown in inactive-torch-blocking-signal.png but without the leftmost torch.
2. Put the torch on left.
3. The redstone wire on the ground now gets inactivated as if it's no longer connected to the rightmost torch.

The circuit in this state behaves very unnnaturally:

1. Remove the torch on the center block. The wire on the ground does not immediately notice that it's no longer blocked, i.e. it stays inactive.
2. Trigger a redstone update in some way, like placing another dust next to the unlit wire.
3. The wire now gets activated. It doesn't respond to a block update in general; only to a redstone update so one might call it a redstone-update-detector (RUD).

The glitch was originally discovered by GreatMCGamer in MCPE-11855. I'm re-posting it because it's now closed as invalid.