Given that GP was discussing publicly, on a technical internet forum, the relationship between mathematical provability and truth/existence, don't you think it likely that GP was aware of Gödel's Incompleteness theorem? My concern is that the "actually", and the smiley face, seems, to me, very patronizing. I really don't mean to be attacking you for a small point of etiquette, and I also acknowledge that the main purpose of this thread (the nature of reality) is a bit more important, but I do make this point sincerely. This is something I find a real problem when discussing things with software engineers. I personally hate the feeling of being patronized in public, or of someone replying in public with the implication that I was not aware of something which I am perfectly well aware of. I'm not claiming that the GP is an expert on the Incompleteness Theorem, and I'm certainly not, but that "actually", and the smiley, sound and look awful. We should assume that others are competent and knowledgable on the subjects they talk about until given evidence to the contrary.

I believe you've misconstrued d13's intended meaning. In short, what they said is something can be mathematically consistent without being physically realistic. GIT is not really pertinent here.

Gabriel's Horn is probably more appropriate: https://en.wikipedia.org/wiki/Gabriel's_Horn