When a piston is powered indirectly (weakly powered) by sitting next to, on top of, or below a directly powered (strongly powered) block, it will cause an attached redstone torch to be turned off. The piston is the only redstone component that exhibits this behavior, and does not occur with the other items that a redstone torch can attach to:

• Droppers
• Dispensers
• Redstone lamps

While this can be potentially useful in certain circumstances, the behavior is inconsistent, and is in direct conflict with the intended behavior of powered vs. activated redstone components.

Additionally, the indirectly powered piston will NOT power/activate any other redstone components, including:

• Redstone dust
• Repeaters
• Comparators
• Redstone lamps
• Pistons
• Droppers
• Dispensers

Any and all instances of piston(s) above includes sticky pistons. The behavior is identical.