Earlier quoted context omitted.
Runaway greenhouse effects on other planets have resulted in surface temps of 400C+
Is there a possible scenario for that on earth, that results in every place on earth having a temperature non survivable by humans?
On whether it's probable, I'd lean towards no but I'm not qualified. The certainty that I read in the parent comment was mainly what I was pushing back against. On a re-read though it's much less certain (either edited or perhaps I massively misinterpreted it the first time around). Runaway implies positive feedback which is hard to gauge, was all I intended to say