I'm fairly certain you could find people implicitly arguing for some varieties of non-subjective relativism. For example, cultural relativism advances the view that one's culture determines the facts about ethics for oneself, but it's not necessarily mental acts on the part of persons in the culture that determine the facts about ethics. Similarly, Divine Command Theory will give you different answers for different gods, but it's not the mental acts of the persons involved that determine the facts about ethics.
It's an interesting question. The SEP link in Jack's comment actually gives Divine Command Theory as an example of non-relativistic subjectivism. It's subjectivist because what is moral depends on a mental fact about that god — namely, whether that god approves.
It's less clear whether cultural relativism is subjectivist. I'm inclined to think of culture as depending to a large extent on the minds of the people in that culture. (Different peoples whose mental content differed in the right way would have different cultures, even if their material conditions were otherwise identical.) This would make cultural relativism subjectivist as well.
Less Wrong is extremely intimidating to newcomers and as pointed out by Academian something that would help is a document in FAQ form intended for newcomers. Later we can decide how to best deliver that document to new Less Wrongers, but for now we can edit the existing (narrow) FAQ to make the site less scary and the standards more evident.
Go ahead and make bold edits to the FAQ wiki page or use this post to discuss possible FAQs and answers in agonizing detail.