So to summarize: There are no positive effects for people who vote porn. Therefore nobody does.

People will follow and yes, upvote the content that is popular. If a dporn bot is upvoting i.e like dmania, dtube and the rest do people will follow it to earn curation. People will use alt accounts and build them up overtime solving the , "don't want their friends and followers to know what porn they upvoted" issue. We already see that with a few other apps. Also, if you have a stake in the platform via the PornD tokens you'll earn 90 % of the rewards the site earns. There is incentives to be on the Dporn platform.