If muscle weighs more than fat...

[malkin]

Neither the OP nor anyone else said that a "pound" of muscle weighs more than a pound of fat.

A liter of muscle DOES weigh more than a liter of fat. And that's exactly what she was remarking on.

Right.

Go to the grocery store and compare the sizes of a pound of butter, a pound of cheese and a pound of the leanest meat they have. Check the size of something that is mostly water too--like produce or juice.