Pistons will become powered if a redstone torch is powered and is 1 block above the piston on the sides or 2 directly above the piston regardless of any lack of connecting redstone or blocks. Redstone blocks work but only when a spacer block connecting is removed or pushed. Afterwords the redstone block will power a piston that is 2 blocks below it even when moved. If the redstone block is moved/destroyed the piston will remain active until updated. Meanwhile the redstone torch will turn on and off the piston as it does.
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Thank you for your report!
We're tracking this issue in MC-108, so this ticket is being resolved and linked as a duplicate.
That ticket has already been resolved as working as intended, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.
If you would like to learn more about this particular feature, see this article on the Minecraft Wiki.
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