Oh I was very on board with the sarcasm. Although as a graduate of one of them, I obviously can't believe you're rating the other one so highly.

This is a general principal

Principle* — unless they're the head-teacher of a school, the type to be involved in a principal/agent problem, or otherwise the "first"

graduates of the great English universities (both of them)

Shots fired

That definitely looks like the one. Appears I'd forgotten some of the context/details though.

I could swear there was a similar Scott Alexander post, about flirting deliberately skirting the edge of plausible deniability to avoid prematurely creating common knowledge. With an analogy to spies trying to identify a fellow operative without overtly tipping their hand in case they were mistaken and speaking to a non-spy.

Can't find it now: might have since been deleted, or might have only ever existed on LiveJournal or Tumblr or something.

https://slatestarcodex.com/2017/06/26/conversation-deliberately-skirts-the-border-of-incomprehensibility/ is similar but not explicitly about flirting.

The strategy above makes all three statements seem equally unlikely to be true. Mathematically equivalent but with different emphasis would be to make all three statements seem equally unlikely to be false.

i.e. Pick things that seem so mundane and ordinary that surely they must be universally true—then watch the reaction as it is realised that one of them must actually be a lie.

I suspect there has to be a degree of mental disconnect, where they can see that things don't all happen (or not happen) equally as often as each other, but answering the math question of "What's the probability?" feels like a more abstract and different thing.

Maybe mixed up with some reflexive learned helplessness of not really trying to do math because of past experience that's left them thinking they just can't get it.

Possibly over generalising from early textbook probability examples involving coins and dice, where counting up and dividing by the number of possible outcomes is a workable approach.

I know someone who taught math to low-ability kids, and reported finding it difficult to persuade them otherwise. I assume some number of them carried on into adulthood still doing it.

In the infinite limit (or just large-ish x), the probability of at least one success, from nx attempts with 1/x odds on each attempt, will be 1 - ( 1 / e^n )

For x attempts, 1 - 1/e = 0.63212

For 2x attempts 1 - 1/e^2 = 0.86466

For 3x attempts 1 - 1/e^3 = 0.95021

And so on

Ironically, the even more basic error of probabilistic thinking that people so—painfully—commonly make ("It either happens or doesn't, so it's 50/50") would get closer to the right answer.