I guess I'll allow that death is the ultimate undesirable thing, disrupting all intentions, negating all possibilities.
I can see how this could be interpreted as unusually high tolerance for suffering, by any normal, latently suicidal person. But from my point of view you're just all getting it wrong. I've never heard anybody else express this position, though, so perhaps I'm an irrelevance.
Late edit: there's more to preferences than mere experiences, mind you. So "I prefer that I not exist" makes logical sense, but not by the reason "because my experiences are so horrible": perhaps some philosophical notion could be the reason for it, though I can't imagine one. Oh, self-sacrifice to save others, for instance, or for knowledge in the abstract, that kind of thing.
I logically prefer than I had never existed, because existing is what exposes me to the cycle of suffering, and I cannot prevent suffering with any certainty. The opposite - this inability to prevent suffering is itself a source of chronic low-grade suffering known to all as "anxiety".
But... I've found myself here anyway! Furthermore, having been born an animal, I find myself bound here by my self-preservation instinct. So, the ethical thing for me to do would be to try and reduce that suffering which I observe. Am I succeeding? Honestly, I don't think I am. (But it's a source of meaning regardless.)
Can I imagine a life without this background of suffering? Only vaguely. Being able to imagine it may itself be a source of suffering, even if I were to accept that it's in fact beyond reach.
I don't think it would be possible to set a threshold for "what counts as suffering", since suffering is an interior experience. It would be the same as attempting to measure consciousness; you can measure its external manifestations, but not the thing itself.
Besides, who would be doing the measuring? Who would be systematizing the results? Who will be interpreting them? None other than beings who are themselves part of the cycle of suffering. So, even if the measurement was to be possible, and communicating its results was to be possible, it's impossible to avoid the data to be biased -- such as by the measurers' self-preservation instincts. An objective measurement can only happen from outside, and... there is no outside.
(I'm imagining maybe dystopian but I would hope at least comprehensible scenarios, such as a state-level actor developing the science enabling them to establish a (purportedly) objective scale of suffering, but then forcing the measurers to publish biased results under duress, in order to promote that state's self-serving agenda.)
Hence, I work with a simple and abstract distinction: less preferable = more suffering. So, not between 1 and 2 -- which communicates exactly as much meaning as 0 and 1, only at a greater cost, think vacuum tube bias voltage -- but fractionally between 0 and 1.
Where the threshold lies for the self and others to recognize that suffering, much less to take it into account, is entirely up to the perceiver(s) in question, and not something that could be irrevocably defined by fiat.
