The bug

The lit redstone torch models in the repeater and comparator texture are missing their bottom texture. Actual redstone torches, normal torches (on a block or at the side of it) and unlit redstone torch models on repeaters and comparators (when the repeater/comparator is unlit or when the comparator is not in subtract mode) the bottom texture is in its place.

Since that texture actually can never be seen ingame unless in spectator mode, it should probably be removed for unlit torches instead of being added to lit torches.

How to reproduce

1. Place a repeater/comparator
2. Lit it (or put it in subtract mode for comparators)
3. Go to spectator mode
4. Go into the block under it
5. Look up

To see the difference, you can unlit it and look again.