Here is the post in question. Should you be blocked by this person, you can open this page in a private window (which should mean you won't be logged in) in order to see the text.
Quoting the post in its entirety, though only the second paragraph is specifically relevant here.
I mean, Snarf Zagyg does it all the time. They've blocked me so I rarely see it anymore, but they and others specifically use hyperbole to make a point and to attract attention. I'd say I've caught yours!
So. If the middle is feeling excluded, let's try to meet with it, yes? I consider it to be precious in the extreme for a GM to nail down so much of their setting that they cannot conscience any form of alteration or expansion. One of the greatest joys of fantasy is the mystery of what lies beyond the horizon, and one of the greatest benefits of playing a living game (as opposed to a computer game, or a prewritten adventure) is very specifically the ability to respond to new ideas, to adapt and grow and improve.
It is difficult for me to understand, then, why anyone would be absolutely unwilling to have a conversation about stuff, and doubly so why they would reject that key benefit, openness to new revelations or developments. You have said that you welcome player participation in terms of actions performed, but have more than once specified that you have pretty strict limits on what is allowed and what makes sense. I struggle to understand how this actually squares with supporting player freedom and the experience of the fantastical.
Conversely, I do understand that merely throwing things together willy-nilly isn't good or productive...which is why I don't do that, and never have. I think through components of the world very carefully. If an additional element is sought, I dig as deep as I can into why it is sought, into how those desires can be met, and (what is most important in a long term sense) how that element will interact with the rest and what consequences that might have.
As an example, I had told my players that I wanted Jewel of the Desert, an Arabian Nights styled game, to not feature demons or devils too prominently early on, and made clear that there are no dragons natively in this part of the world. (The aforementioned time dragon is only the third actual dragon character that has appeared in over four years of play. I have shown great restraint!) Then, however, one of my players asked to play a tiefling. I knew he wasn't going for something disingenuous or subversive, that's both entirely the opposite of his personality and kind of difficult to pull off in Dungeon World. Instead, he was expressing his sincere interest in something he found cool. So we talked about it. I told him (more or less), "So, you wouldn't experience systemic racism here, because I'm following the lead of Al-Qadim on this, but it is possible you've had individual racism issues. Further, being connected to forces like this may matter. Who is your tiefling parent?"
His answer set a major component of the campaign: "I'm cool with that. And, uh, I was actually thinking both of his parents were tieflings? I'm okay with whatever you want to do on that front. I was thinking his mother's maternal grandmother was a succubus." (Again, paraphrased.)
The mystery of who his paternal bloodline's devilish ancestor is remains unsolved, but they know it's gonna be a spicy meatball when they find out. (They've narrowed down his ancestors to either Baalzephon, a Pit Fiend and former prime minister in Hell, or Prince Glasya herself.) By not taking a hardline stance, and instead taking the player's request, considering it carefully, exploring the implications, and then accepting it, the campaign was significantly enriched.
That's the kind of thing I would like to see. Careful consideration, earnestness, genuine discussion and not fiat declarations and "c'mon, don't you trust me?"
