Spam will come in anyway. The problem is easy to see on steem. The rewards doesn't matter. There will come link spam if no active curation happens.
That's what on steem happens.
IMO on hive the problem is not that big as on steem. Because the community manages it.
If the first SEO tools include hive, like gsa T2 /T3 and other ping/spam tools, there will also spam happen here.
But this is not linked to rewards. It's all because of search engine optimization. Special SINA ( China search engine and the Russian one).
The algo doesn't penalty spam links in the same way as google does.
to prevent, the easiest way would be:
Reputation under xyz = link is blank, no hyperlink, or link + low reputation = comment doesn't show up.
So downvotes matter in the case of reputation busting from spammer.
Reward farms get easily downvoted IMO. And are not worth the effort. There is more money made by spammers with affiliate spam + hide link direction via buffer side.
Noobs will always try :) No matter what we do :D