I think he means that if he has selected a bunch of vertexs and then marquee select the top part of the model, only the vertexs inside of the marquee gets selected/deselected (if not selected, select and the other way.) Imagine if you have a 3x3 plane and select left and right side, so you have two columes selected and…
hold alt? Or am I misreading something :o How would a inverse marquee selection work exactly? Do you mean like selecting a bunch of stuff and then using ctrl+I for inverse, all in 1 single action instead of 2?