I raised this concern I had on the old flarum forums, and no solution was found and it was lost when Seth deleted the forum.
New accounts should definitely not be allowed to vote on pretty much any poll. The fact that we also use public voting for a majority of our decisions such as forum staff positions, exec approvals, and server additions should also concern you. I don't really think I need to explain why this shouldn't be a thing.
Im fairly certain this was a feature on proboards, because as forum admins could see who voted on polls, I regularly checked and newly created accounts never voted on polls. If there is not an extension, or a fix, we should really refrain from continuing to use flarum polls.