The bug

One single redstone dust powered by either type of redstone comparator and pointing any container that reacts to redstone signal (e.g. item hopper) does not properly connect to redstone components including:

• output ends of redstone repeaters
• output ends of redstone comparators at the same or lower power level
• unpowered redstone dust
• redstone torches (only when the dust is at 15 power)
• flank ends of redstone comparators

the list above may not be complete

the PP updates do properly cover the redstone dust and can be detected by observer

How to reproduce

Create the setup shown in the image below. The chest should contain a single item, and the bottom redstone wire should be placed last.

Expected behavior

The two pieces of redstone wire should be connected.