Boom Boom

U suppose that MC-2255 is the problem here. When I was looking for tickets related to it, I only searched for pistons, I didn't think that this might somehow be connected to visual indicators not being in sync with underlying mechanics.

Since this is the case, I suppose it doesn't matter which way it swings: whether the power is diverted from the lantern and directed onto the piston, or whether the textures/models change somehow to indicate that the power actually flows straight to the next block and also up to the block above on the side, but not to the block underneath it (on the side, on the same level as the redstone conduit). The real problem is that there's only one way to convey the flow of power to the player, by the visual display, and the way this visual display works does not convey it at current moment because the way these things are displayed is not consistent between different use cases. To achieve consistency, either the way redstone transitions are displayed has to change, or the way power travels through redstone lines has to be changed, or both have to be changed. Unless, of course, consistency is not pursued in this aspect, and this becomes a moot point altogether, so we can simply document the way it works, agree that it's the correct behaviour, and move along.

Redstone can power blocks from the side, and when the wire is not bent towards the block, but runs straight at it, the pistons get powered. Consequently, consistent behaviour would power the piston, the piston would extend, the wire would straighten, and the piston would stop being powered. Like so: