So, not sure how to describe this properly, but I definitely have video.
Messing with redstone, found a strange block update behavior that activates while setting a redstone in a Chess Knight's position away from water connected to an observer facing toward the Water or Lava.
Breaking just one piece doesn't disable it, but both will.
Adding just one back won't enable, both have to be present.
I am so confused.
Sorry for the lag on first video, encoding issues (fixed in the second, using lava for a slower pulse)
Umm.... No.
The water doesn't re-trigger the observer in this case. It's the interaction between the redstone and the water causing an update over several blocks. You can see that the second observer is not connected, like in the screenshots of MC-109829. Also, is only detectin a source block, which I understand is supposed to update when a block next to it updates.
To the best of my redstone knowledge, the redstone being placed behind the observer isn't causing the observer to update, but rather the block state of the redstone dust being changed that causes the observer to update, temporarily. This is why taking the last redstone dust away again causes the "machine" to still function.
I mean, unless the cause is the same, but the understanding is quite different in the linked Issue.