If we could have moving solids, we'd have done it by now because they'd be very useful. However, we cannot, so we... uh... can't have them...

@Physics3000
everybody always says "no moving solids", but never explain why, which probably confuses you, yes? well its pretty much impossible to code movable solids, and if anyone tried, it would probably result in horrible bugs with gravity, viscosity of liquids, how anything would react to the solids, and having to switch that setting on and off would produce way too much lag, its just way to complicated for the coders, and for the slower computers running TPT, so although it is a good idea, its just unrealistic for the technology we have today, sorry.

Then why not just adding this in FAQ?

At least 1 from 1000 will look in it.