Exactly. Thread over, there's really no need for a rules other than general laziness.
No, tools that streamline things can be more important then making tools that do new things.
For instance, using a ghost brick requires you to switch away from the current types of bricks you are using. It also does not stick around after you switch back to the bricks you are using. If this "Ruler" tool was done right, it could even leave several markers behind.