If the position is abutting an end of line marker, it moves past it, to include it. If not, it does nothing.

The intention is so you can delete a whole line by doing:

with(selection) {
	moveToStartOfLine();
	setAnchor();
	// this moves to the end of the visible line, but if you stopped here, you'd be left with an empty line
	moveToEndOfLine();
	// this moves past the line marker, meaning you don't just delete the line's content, it deletes the entire line
	moveToIncludeAdjacentEndOfLineMarker();
	setFocus();
	replaceContent("");
}