Nethack runs as a setgid process that hides save files from users.

Kind of old fashioned now that almost every Unix system is a single user system. There are still public servers for those that want the temptation to be taken away from them.

As to spoilers... Everybody reads the spoilers. I doubt anyone has ever ascended spoiler-free.

[Possible obscure spoiler]

A friend once showed me a post on rec.games.roguelike.nethack where someone was finally begging for a hint because they'd gone deep in the dungeon and couldn't figure out anything to do next. They couldn't find any staircases down, though they had found a weird vibrating square, and none of the many weird items they'd collected seemed to do anything to help.