The dreaded double post? I'm not even sure how you guys create those.
Clicked quote instead of modify, meaning a second post consisting of me quoting everything in the first post. Except, y'know, with better language use. Dunno how other people find themselves double posting, but I think that's always how I get there.
And one of those hang ups is your personal criteria for what or or isn't a rules source which appears to be erroneously based off a system for handling rule contradictions. In your post you reach back to the outdated primary/secondary idea, it is a concept was introduced and depreciated by the Errata over how to handle when two rules disagree with each other the more specific source becomes the "primary" entry and what it says holds priority over the rest.
How are the primary/secondary rules outdated? And, whatever the purpose of those rules, they seem to indicate that the FAQ is superseded by other sources where the two conflict.
But that has nothing to do with what is or isn't part of the rule structure and this is also why getting into your fourth paragraph your points become less defined and try to latch on title wordings and implications.
The reason my points become a bit less defined there is that there's really not that much to argue over. Aside from the title, nothing I'm aware of indicates that the FAQ is part of the fabric of the rules, or indicates that it's not a fabric of the rules.
Let's shift the topic. What gives the Errata the right to edit the PHB?
It's indicated by two of the things you list below, and you don't.
You might say because the text says it replaces the PHB, well what gave it the right to say it can replace that text?
Rules text inevitably has to give itself authority, because it's not going to come from anywhere more important. Had the FAQ such text, then I'd agree that it does qualify as a source of rules, or as something that's explicitly altering past rules. But it doesn't, so it is neither. It is a fundamental paradox of rules that the text is essentially giving itself authority to give itself authority, but that's the source of authority we have.
You might say the page you download the Errata from, except that's simply "D&D Updates".
Well, yeah. Updates to D&D. That's what the errata is. As I said before, a header of that sort instead of the one that exists for the FAQ would supply you a much better argument.
And when your stance is not all products are inherently rules, then updating a product of D&D does not automatically mean the update is a rule either. The same problems you feel you have with the FAQ echo in relation to the Errata.
Some arbitrary product isn't necessarily rules. An update to existing rules, however, is necessarily rules.
So, it's those two things. The language within the errata, which strongly implies that the errata takes precedence, it's the D&D update header, which, in a way that is not the case for the FAQ, implies that we're altering the rules here. And, critically, you don't. That last factor being, this is just what errata is. An FAQ is meant to adjudicate ambiguities, or, if there is no ambiguity, it's supposed to state the existing rules in a clear cut way. Errata, meanwhile, is by definition, a list of errors and their corrections. Errata is meant to correct the text in a way that an FAQ really isn't. In these ways, any asserted parity between the FAQ's rules status and the errata's rules status breaks down somewhat. They're different entities.
The Errata's authority to edit the existing books is issued to it by being included in the rules system by the game rule page. From there, it gains the official status to claim something like the text on PHB 123 should read "Where forever for". Now again, it's important to note that the Game Rule designation only enters it into the rule structure. You are in turn are to obey all rules set forth by the game.
Except it's not on any game rule page, for one thing. For another, whether this is part of the rule structure or not, it doesn't necessarily have any authority within the rule structure, as I will note below.
This can become problematic when one rule says you may do something and another says you may not. You, by default, have no authority within the rules. When something says yes and something says no you do not have an inherent claim to differentiate between the two, much like you do not have the inherent ability to claim what is or is not part of the rule structure. All you have is what the rules expressly give you, and the largest tenant of which is the Order of Rules Application.
And that tenant is where you are getting your primary/secondary stuff from except does not bestow you the ability to exclude something from the rules. Even if two things contradict them selves, the tenant does not remove one of them but designates which is more correct. So I feel like we have to talk about this area some more too, but later.
Indeed, I personally have no exclusion ability with regards to the rules. The RAW moves between three states in the adjudication of a pair of contradictory rules. A can be right, if it has precedence, either by specificity or by primacy, B can be right, for the same reasons, and the situation can be ambiguous by RAW, if neither source has clear primacy or specificity. I do not have the ability to adjudicate anything beyond what is stated in the rules, but the rules do have exclusion ability with regard to themselves, and primacy is a part of those rules. You may read primacy as keeping the FAQ around, but never picking it, or you can read it as full exclusion, but either way the end result is the same.
So, in that sense, you might be right. Maybe the rules just don't include the FAQ, which is possible because of the header, or maybe they do, and every time the FAQ contradicts something it loses. I see the latter as a way more effective argument, so, to that end, how exactly does the FAQ win a fight? The RC can because it explicitly says it can, the errata can for all the reasons stated above, but how can the FAQ win? The way I see it, by this argument, is basically the way Link saw it earlier. The only way the FAQ could possibly alter the rules is if those rules were strictly ambiguous, because then it wouldn't have anything to contradict, but in those cases you'd have to prove that strict ambiguity. Does strict ambiguity exist as applies to warlocks? Maybe, or maybe not. It's a non-trivial thing to prove, in any case.
I think I need some historical context. Is there any particular reason to ignore the FAQ? I don't mean "are there builds that ignore the FAQ or groups that ignore the FAQ," since I am sure there are, but unless somebody at WotC outright said that the FAQ should be ignored, then it shouldn't be. Because if the FAQ was not meant to be used, then why on Earth would Wizards of the Coast even write it?
If someone chooses to ignore what was intended to be used, couldn't one also ignore whatever else, including the PHB? If the designers say that this is how the rules are supposed to work, then you can be sure that this is, in fact, how the rules are supposed to work.
D&D is a game written for ordinary folk, not software programs. The Law of Common Sense should come into play at some point.
There're a couple of reasons. The stuff I said above was important because it's the rules justification for ignoring the FAQ, but the "reasonable man" justification has a lot more to do with the fact that the thing just directly contradicts RAW. How am I supposed to take it when the FAQ is answering my theoretical questions with objectively wrong answers? Ostensibly, one writes an FAQ for the purposes stated above, adjudicating ambiguities and correctly re-answering questions already answered by rules. Unless stated otherwise, it's not meant to be a weird errata for errata. I don't have a great list of all the weirdnesses of the FAQ, but were it a less strictly wrong document in some cases, then I doubt we'd be having this argument.
As a quick example, it'd be if someone were like, "I'm too lazy to check myself. when do fighters get their bonus feats, and how many do they get?" and then the answer given is, "I'm glad you asked. Fighters get ten bonus feats, one every odd level." How would you take that? The answer wasn't even saying, "While the original text said..." it's just coming out and saying outright incorrect information. Would you say, "Yeah, that thing in the FAQ, as opposed to the information visible directly before my eyes in the book, is probably right," or would you assume that the PHB has the right of it, and the FAQ just missed something? How do you even work through that? It's such a weird situation.