Although there were exceptions. If you got hitched to a high-visibility program, failure was considered a sabotage.

So I guess the best position in a communist country is to be extremely useful and extremely obscure.

You could say that. I'm from Poland, so compared to Soviet Union it was communist-lite. I had a brilliant math teacher in high school. He had the reputation that if he was your math teacher you were automatically accepted at the local university. He was a legend in my town, and managed to stay under the radar of the communist regime.