I agree plausibility is technically required for circles - but in many of the examples I see for Circles - plausibility is such a minimum constraint that it might as well be non-existent.
I've given two examples in this thread, from Burning Wheel play: Thurgon (together with Aramina) meeting Friedrich, and Thurgon (together with Aramina) meeting Rufus.
I may also have mentioned a Torchbearer example: Fea-bella the Elven Dreamwalker reached out to her friend Glothfindel in her dreams, and realised that he had been captured by Megloss (mechanically, the player wanted to meet up with Glothfindel the ranger to help the PCs trek through the wilderness, but the Circles test failed and so I narrated the kidnapping instead).
Which of these do you have in mind as illustrating a constraint thatis "such a minimum . . . that it might as well be non-existent"?
Circles as far as I can tell doesn’t have plausibility factor into it in this way. You have the same starting chance for circles to succeed no matter whether it’s very likely or just kind of unlikely.
Have you ever played Burning Wheel? Read the rules? Even read my posts about it (I am the only poster in this thread who is discussing their actual play of this RPG.) Here is one about setting obstacles for Circles tests:
I am only speaking for Burning Wheel, as far as Circles is concerned. (Torchbearer also has Circles, but it is a different system which gives the player less agency than does BW - something I have noted multiple times upthread.)
There is a rule for establishing the obstacle. Everything else being equal, it is easier to meet a "generic" person than a person who is ready to give you resources for nothing. Likewise, it's easier to meet someone vaguely helpful as you're travelling along, than it is to have someone in the crowd ready to rescue you just as you are about to be executed.
Setting Obstacle level seems to reflect taking into account varying fictional plausibility levels. So appears the mechanics do take that into account for determining chances of success.
You don't say!
Does it require "radically transparent intent" in the book? I don't hold blog posts as binding.
How many posts of mine stating the "intent and task" rules have you read? And if you're worried I'm misquoting them, you can download them for free and read them yourself:
Burning Wheel Gold: Hub and Spokes - Burning Wheel | Burning Wheel | DriveThruRPG.com
For example - you might circles a doctor or apothecary in the town nearest you for a healing potion. Very plausible (requires a few assumptions about healing potions in the fictional a world, but mostly plausible for a fantasy fictional setting).
However, you might instead circles a farmer for a healing potion. Less plausible but not totally implausible. Is that an acceptable circles check? I’d not, why not?
If farmers are in your Circles (ie you have a Peasant lifepath), then yes. The minimum obstacle would be Ob 4 (base 1, +3 Ob for "a specific disposition or detailed/rare knowledge") - in this case, what is specific/rare is that the farmer in question has a healing potion.
The obstacle will be higher if the PC hope to meet this farmer
right here and now. I'm thinking of a counterpart to the scene in the film Ronin, where Jean Reno takes Robert De Niro to his friend's house, to perform surgery. In Burning Wheel, I could imagine a hard Ride test ("We had to be there yesterday!") and then a desperate Circles test ("Someone in the hamlet must have a healing potion stashed away - I hope they'll help us!").
I don't understand why this is supposed to make for bad RPGing.
Most notably - player can shop around till he gets better than normal chances, since players don’t have to commit till they know the odds and what the consequence will be.
Have you read or played Burning Wheel? This claim is false.
From p 248 of the Adventure Burner (which is reprinted in The Codex):
Once you've stated your intent and task, once your character is in motion and the obstacle has been presented, you're expected to roll the dice. Even if it's too hard! . . .
Any negotiation about the appropriateness of the action should be handled when you state your intent. Any questions about rules clarifications and obstacles should be handled before you get to the intent stage. . . . An obstacle isn't a physical thing. It's a metaphor. Once it's presented, you need to confront it!
In other words, the rule is actually the opposite of what you've stated.
I've only read Burning Wheel not played it but if I remember right there's a strong presumption that the Circles check is about something important to the character and the GMs' principles include that they should direct play at things important to the characters.
Agreed. Though how directly they should relate seems to be up in the air?
How is it "up in the air"? I've quoted the rules text in this thread (probably from Revised, but the text in Gold and Gold Revised is mostly identical in words, and completely identical in spirit). Eg Revised pp 12-13:
players take on the roles of characters inspired by history and works of fantasy fiction. These characters are represented by a series of numbers, designating their abilities, and a list of player-determined priorities. . . . The conflicts of the characters aforementioned priorities create situations for the players to resolve, and resolving conflicts (and creating new ones) is what play is all about.
I've even posted examples, like Thurgon and Aramina's meeting with Rufus!