"Shift right click to remove the selection. Hold ctrl to highlight a block in midair and Scroll to adjust the distance. Once two blocks are selected, look at the selection's faces and ctrl-scroll to adjust the size."

Trying to follow these directions after having swapped run and crouch leads to being about to highlight blocks in mid-air, but when you try to right click and finalize the selection, it is deleted instead. It seems like ctrl remains the "highlight a block in midair hey" but that shift gets remapped to ctrl for "remove the selection" Like one is set to literally always be that key and the other is actually whatever crouch currently is.

I think it's insane that Minecraft defaults to ctrl to run when so many games default to shift so I could see this affecting a lot of players.

Mixing hardcoded and remappable keys like this is just bad design, it should be changed so either clear selection is hardcoded to shift, or midair selection uses the remappable sprint key.

If this still occurs on 0.5.1f open a new issue