I knew a sysadmin at a different job who did that. And since MUDs were text, many in the office at the time had no idea what was on his screen.
And to your point about high-demand/high-stakes, at the same job as the MUD guy there was an old guy. He would leave before lunch go play tennis, nap under his desk in his cube, etc... I asked one of the other young people one day (I was still in college), what the old guy did. Apparently he was the only one who knew how to code a certain system, and he was only there to do that job when the system needed a change or had a problem.
And to your point about high-demand/high-stakes, at the same job as the MUD guy there was an old guy. He would leave before lunch go play tennis, nap under his desk in his cube, etc... I asked one of the other young people one day (I was still in college), what the old guy did. Apparently he was the only one who knew how to code a certain system, and he was only there to do that job when the system needed a change or had a problem.