> the fact there are two pointers on the screen -- one for the mouse and one for the keyboard -- if you slide the mouse pointer to a specific point and press a keyboard key, the new key will not appear where the arrow is, it will appear where the text cursor is.

I remember using an (early?) Apollo computer that worked that way... I was warned by the person showing me, and a bit later he accidentally bumped the mouse while I was typing! Letters all over...

I believe this was in the era before X windows took off for unix boxes. I miss SunTools - it was nice and simple.