I also participate in several sites across the SE network. What I see is that this site is one of the most difficult ones. It seems that Philosophy Q&A is hard. Why? Because we are not philosophers, in the sense that the idea of this site is not to do philosophy, but to discuss it. Especially, we always encourage people to provide references to their answers.
You're saying in your question here:
[...] nowhere have I seen so many users acting as authorities (prescribing to other users what they should do, discussing questions/answers from the point of view of relevance for the site rather than expressing their own opinion about the content or just appropriately flagging/voting with an explanation).
Discussing the relevance of posts is 1) because of the above, that Philosophy Q&A is hard, and also 2) because it's typical for a beta to still try and find out what posts are well or ill suited for the site.
That being said, you complain about users acting as authorities. I take it that you are partially talking about me, considering our discussion here. For me it's always easier to take an example, so I'll take this one - if this is not what you meant, please tell me, and show another example.
Your answer in question was:
Having free will means nothing more than not knowing yourself what you will do (or will want to do or will try to do) in future. Even if all of your actions are perfectly known beforehand to everybody else but you you still have free will.
My first comment was:
References, argumentation, ...?
Normally I write a longer comment with a link to the help center or meta. In your case I didn't because you had shown before (1, 2) to be quite stubborn anyway. But considering you're active on more SE sites you should know that we like answers to be supported by references. This is also the way it works in most other contexts (e.g. academical).
So basically with this comment I did exactly what you want: I expressed my opinion about the content and flagged the post accordingly. You then started discussing so I supported my claims with three references: 1, 2, 3. Now you can say you find those references irrelevant, but you can hardly call this acting as an authority. I gave you the references to support my claim: meta and the help center. If you want to dismiss a meta post of one of our moderators with score +12/-0 because it's only a meta-question, that's your decision, but it's not really how it works here.
Essentially, I don't really see what you mean. Users acting as authorities? Not really. We provide references to meta and the help center as much as possible to help you write better answers. In this case I invited you to chat to discuss it further, which you for some reason ignored - that's fine though.
Every SE sites has its own ins and outs concerning what are good questions and answers. You can have a million reputation on some other site, if you come here for the first time, you'll have to learn our ins and outs. There's a small vast user base here which is very willing to help you with that. It is the idea of communal work.