An important distinction the README doesn't really express is that any features like this are tied to the position of the text cursor inside the character grid,

An important distinction the README doesn't really express is that any features like this are tied to the position of the text cursor inside the character grid, not to the position of the mouse (though of course they may accept mouse commands similar to how xterm does). They are GUI-like, but they are the sort of GUI-like things that programs like vim and emacs already emulate all the time.