This is an interesting topic, I would like to discuss further.
Locking down votes to accounts on the instance is important - the current system of Aye/Nay comments natively beats strawpoll on that account.
Since this instance is anonymous, having some amount of accountability to other users is also important. Even I can go through and at least audit comments to be sure they're on the instance and active users. This is another point where, again, strawpoll falls short.
I agree the system isn't perfect, but IP locking is also an imperfect solution. There are absolutely VPN solutions that will beat strawpoll's VPN identification, and there very well could be legitimate votes that would share public IP addresses, especially as the instance grows. I think I'm unconvinced that ensuring unique IP is vastly more important than the benefits the current system provides.
All that said, I don't know what a perfect solution would look like, but I would expect it to address ALL of these points (deep integration with lemmy, user auditability, and basic protection from fraudulent votes). I'm honestly curious what your thoughts are here - do you have a more comprehensive proposal to address my above concerns?