You're demonstrating a comprehensive lack of actual domain knowledge - you literally don't know the thing you're talking about - and appear to be trying to compensate for that by leveraging what you do know.

As far as I can tell, everything Yvain has said on this topic is correct. In particular, there is a further possible assumption under which it is not the case that cosmic ray collisions with Earth and the Sun prove LHC black holes would be safe, as you can find spelled out in section 2.2 of this paper by Giddings and Mangano. As Yvain pointed out in a different comment, to plug this hole in the argument requires doing some calculations on white dwarfs and/or neutron stars to find a different bound, which is what Giddings and Mangano spend much of the rest of the paper doing. These calculations, as far as I know, were not actually published until 2008 -- several months after the LHC was originally supposed to go online. It's my impression that both before and after this analysis was done, most of those arguing the LHC is safe just repeated the simplified argument that had the hole in it; see e.g. Kingreaper in this thread. And while I'd put a very low probability on these calculations being wrong and a very low probability on the LHC destroying the world even if the calculations were wrong, it's this sort of consideration and not 1 in 10^25 coincidences that ends up dominating the final probability estimate. Then there were all these comments about the LHC causing the end of the world being as unlikely as the LHC producing dragons etc -- which if taken literally seem annoyingly wrong because of how the end of the world, unlike dragons, is a convergent result of any event sufficiently upsetting to the physical status quo. So while (just because of the multiple unlikely assumptions required) at any point and especially after the Giddings/Mangano analysis a reasonable observer would have had to put an extremely low probability on existential risk from LHC black holes, the episode still makes me update against trusting domain experts as much on questions that are only 90% about their domain and 10% about some other domain like how to interpret probabilities.

I don't know if you're on board with the Bayesian view of probability, but the way I interpret it, probability is a subjective level of confidence based on our own ignorance. In "reality", the "probability" that the LHC will destroy the Earth is either 0 or 1 - either it ends up destroying the Earth or it doesn't - and in fact we know it turned out to be 0. What we mean when we say "probability" is "given my level of ignorance in a subject, how much should I expect different scenarios to happen".

So when I ask "what is your probability of the LHC destroying the world", I'm asking "Given what you know about physics, and ignoring that both of us now know the LHC did not destroy the world, how confident should you have been that the LHC would not destroy the world".

I'm not a particle physicist, and as far as I know neither are you. Both of us lack comprehensive domain knowledge. Both of us have only a medium-level of broad understanding of the basic concepts of particle physics, plus a high level of trust in the conclusion that professional particle physicists have given.

But I'm doing what one is supposed to do with ignorance - which is not say I'm completely totally sure of the subject I'm ignorant about to a certainty of greater than a billion to one. Unless you are hiding a Ph.D in particle physics somewhere, your ignorance is not significantly less than my own, yet you are acting as if you had knowledge beyond that of even the world's greatest physicists, who are hesitant to attach more than a fifty million to one probability to that estimate.

This is what I meant by offering you the bet - trying to show that you were not, in fact, so good at physics that you could make billion to one probability estimates about it. And this is why I find your argument that I'm ignorant to be such a poor one. Of course I'm ignorant. We both are. But only one of us is pretending to near absolute certainty.