(1) MMI =! "the referee is the final say on the fiction"
I think that many people will agree that the DM/GM/Referee/MC/Lorekeeper/etc. is the final arbiter/facilitator of the fiction, rulings, rules, etc. However, I think that MMI entails the idea that players require asking for the GM's explicit permission for knowing things or doing things, especially those things that are not laid out in the rules. This is to say, I think that there is a difference between (a) players getting knowledge from the GM's scene framing, negotiating the fiction, or asking questions of clarification so they can make informed in-character decisions AND (b) the players having to repeatedly ask for the GM's permission to know or do things for their character.
I think there’s a difference between having the final say and having all the say. The GM roles requires some amount of authority; I don’t think anyone would say otherwise. It doesn’t require total authority.
(2) I believe that your questions here get close to the rub when it comes to character knowledge. This is is something that @Campbell talks about
here: i.e., the dissonance of playing a character who inhabits the world who has to "earn" that common knowledge from the GM.
I had somehow missed this post you linked to, so thanks for that!
To touch on
@Campbell 's point about it being less about authority and more about the alien effect... I kind of see these as related. If what players know about the world, and what their characters know about the world, is indeed gated by the GM, as
@overgeeked said, then I don't see how it's not veering into Mother May I land. I mean, how else could such a situation be described?
The GM tells the players that they see hyena-headed humanoids. The player characters have not encountered them before in gameplay. What is reasonable for the player characters to know without asking for the GM's permission to know about them?
Personally, I'm way past the point where I find any interest in anyone at the table pretending to not know what kinds of monsters they're facing. I simply don't care to do that. So if I introduce these creatures, and my players say "those sound like gnolls" I'll just say "yup, they're gnolls" and call it a day. What's to be gained by keeping that from them?
If they want more specific information... like clues about where such a group might lair, or cultural details and the like... I'd generally rely on some kind of ability check. I usually let the players select the relevant ability and skill. Most such ability checks would be at a medium difficulty, so DC 15 is like my default. I don't really see the need to go with a higher DC for this kind of thing, generally speaking.
I usually limit such attempts to one roll, though. I don't find it fun when there's a roll and it's low, and then every other player jumps in with "I'll try to know that, too" and you get four more rolls. So if there is anyone else who has a relevant skill and would like to assist, then I allow the player who is rolling to do so with Advantage. I find that without that limitation, there's little point to rolling, and if that's the case, then I'd just tell them the information.
My player character is a dragonmarked heir of House Cannith. How much can my character reasonably know about House Cannith (and tangential matters) without asking for the GM's permission to know these things?
I feel like this kind of setting specific thing is best addressed up front to some extent, but that it must be continually revisited throughout play.
You are playing a FKR game of Star Wars: Clone Wars.* Your character says something based on what you think is reasonable for your character to know about the world from their in-world perspective, e.g., based on your roleplay, you think your clone trooper knows about or has heard rumors of the Bad Batch. Your GM disagrees. What then? Do you ask for the GM's permission to know it? Do you try advocating for your character to know it? I'm curious.
Similar to the one above, discuss up front and then continually during play. I generally default to letting players use the knowledge they have in play. One of the reasons to use a known setting like Star Wars or Greyhawk is that there is a lore that already exists and it's fun to engage with that lore. Shutting down that knowledge so that the "characters learn on their own" is, in my opinion, really boring and I'd put in the effort to avoid that kind of thing.
Does this mean there can be no secrets? No, of course not. But that kind of stuff needs to be considered. I think the instinct to make the players work for every scrap of information as
@Campbell talked about can work against the play experience. This is where GM judgment should come into play... what do we as a play group gain through sharing or not sharing a specific bit of information?
Just holding back info as a default approach.... gating that information... is the kind of GMing that starts to move toward Mother May I, and in my opinion, should be avoided when possible and limited at most.
