> If you turned in an assignment written in pencil, it was legit for the teacher to use their eraser and give you an F for turning in empty paper. (They never did this but threatened it a lot).

I find this slightly amusing/ironic because many (most?) fountain pen inks are not waterproof. I had a sheet of paper that was full of (fountain pen written) writing on my desk when I spilled a glass of water -- after the paper dried there was hardly any evidence that there had been writing on the paper. I know that's not the parent's point, but something turned in that was written with a fountain pen would be easier to remove: a teacher would just need to dunk the paper in water!

> many (most?) fountain pen inks are not waterproof.

I assumed this was for child friendliness - you just know kids are going to get ink on their fingers etc while changing cartridges from time to time.

Apparently the inks used in antiquity were not waterproof either. Even though vellum or high quality parchment could last several centuries (if not eaten by moths or other bugs), a single slip of a beverage could erase an entire scroll. Perhaps that's a primary reason that 90% of the works written before the fall of Rome have been lost.

Indeed, pencil is one of the best writing implements for archival purposes. As long as one doens't deliberately try to get the graphite off, it'll probably stay on.