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If it is possible to delegate SP to a third account then just follow the SP delegation chain and restrict upvoting any of the accounts in that chain.

This way the user will only be limited to upvoting friends and cronies and not necessarily their own accounts.

That might work. Yet, it can be done without delegation as delegation didn't always exist. People would power down... send their steem to a different account and then power up that account. They could also do that via an external exchange. So what you stated would likely work for actual delegation but it can still be circumvented using the old method.

Then software "solutions" are merely meant to frustrate rather than completely solve anything.

Well it isn't that they are "meant" to frustrate. It is that people can find a way around most of them. Yet, the end result is that they would technically just be a "frustration" for those serious about exploiting the system. Those not serious and doing it simply because it is easy to do might stop doing it. "Might" being the operative word. Just a guess/speculation.

Theoretically, blockchains can be hacked but the effort required to do so is not worth the attempt at hacking the blockchains.

What needs to be found is a simple solution to create such significant frustration that it is not worth exploiting the system.

I understand I am suggesting a simple solution of a similar leap to that of the blockchain without giving any specifics. This is similar to suggesting there is a simple solution to mind control.

the solution hopefully may be simple... finding that solution I suspect will be very challenging. I am one of those that when I say challenging that doesn't mean I don't think it is worth the effort. I personally think challenging things are often the things that are most worth the effort.