Dr. Bill, I will combine into Wordwind's definition of stochastic that it means also: by guesswork or by chance.
Therefore it would make sense to me that Faldage might have meant that determining what constitutes irony is highly subjective, depending upon (hi, M!) what an individual's experiences and intrinsic mind-set are.

WW, I like that mycterismus word you found. I do hope it's a real word--my little mind has quite enough trouble keeping up with the new real words--I haven't any brain cells to spare to try and learn made-up ones! But it sounds like a combination of mystery, rictus (mind-leap, here), and miasma: quite intriguing!