This has bugged me for years, and it makes absolutely 0 sense 

why is the piston below a powered one always activated as well? it happens no matter how you power it, and you need to do some extra complex redstone just to isolate a single piston in a column, this doesnt occur with anything else as you can see by comparing a lamp cube and a piston cube that both have a redstone block in the middle. I understand that it used to make redstons doors a little bit easier, but now that we have slimeblocks, observers, etc, this BUG needs to be fixed once and for all.