How could a decentralized network limit the amount of nodes to one per user

Proof of Elapsed Time seems like a great idea to me, but in fully decentralized and public networks (like one similar to bitcoin) this would bring problems with it as one could just put up as many nodes as they like to heavily increase their chance of mining a block.

Is there any way to limit the amount of nodes a ‘user’ could run to 1?
Are there any solutions to this problem?

But the first problem would probably be defining what one ‘user’ is