I know of no non-economic incentives for commercial spam. Personally directed spam, such as during a dispute between parties may have other incentives, such as deep and abiding butthurt. There may be other mechanisms potential to reduce such non-economically motivated spam, but I submit that is a tiny fraction of spam and in the vast majority of cases commercial spam that draws flags is quickly and completely dissuaded by the ability of flaggers to completely eliminate any rewards from spam ops.
Just as DV's censor spammers, they censor everyone else that is flagged, too. DV's are taxes because they return rewards to the pool that had been directed to creators exactly as taxes are taken out of your paycheck and returned to the government before you receive it. On Hive everyone with stake can tax anyone to the limit of their stake. Such economic disincentives are a very common mechanism that oppressive governments employ to censor speech, such as fines, and seizing bank accounts, and debanking people that is becoming more and more prevalent. When they are tied to specific speech they often work very well to silence that speech, on Hive and elsewhere. Canada seized bank accounts of people that donated to honking truckers in the attempt to end the Freedom Convoy there, and as I recall that did end it.
Trump has promised John Deere, for example, that if they move their factories to Mexico, they will pay a 200% import duty for their products sold in the USA. Since such taxation is a strong disincentive to do business in ways that are so punitively taxed, when many creators on Hive have been taxed 100% of their earnings, they are similarly discouraged from publishing on Hive. I have provided some such punitively taxed users 5% of my author rewards for years in order to provide them some economic return for their posts that couldn't be taxed to nothing. I have just learned about @commentrewarder, which enables authors to share their author rewards with commenters they upvote on their blogs, which also provides non-taxable income, and am trying that out.