12 point courier etc.
When I used to teach a scriptwriting course I gave the students a rule. If you can't do it on an old typewriter then you shouldn't do it. This also caused a mutitude of questions about why that should be. All my reply consisted of was to emphasis the fact that obeying the 'rules' will ensure you seem professional and your script out of the iffy pile.
But, really, what sort of answer is that??? Imagine telling a DoP he could only use a silent handcrank camera from 1920 to design his shots. If it can't go on a wooden tripod you can't use it!
When will someone just do it. When will they change it. Or does this (and I say this reluctantly) actually help the writer control this stage of pre-production?