Fascinating! Thanks. (to be pedantic, my emphasis on the word "was", meant to convey that my opinion was changing)
I was gonna ask "do you have a source on that?" but was able to find this in JAMA w/o much effort: https://jamanetwork.com/journals/jama/fullarticle/2788346 which states in no uncertain terms that "The rates of myocarditis cases were... in adolescent males aged 16 to 17 years .. 105.9 per million doses of the BNT162b2 vaccine", sure enough, 1 in ~10k.
I think it's also important to note, just for larger context -- not attacking or negating anything you've said -- that that cohort (16-17yo males) is the most extreme, it's down to 1 in ~20k once you include up to age 24. Across the whole population it becomes closer to 1 in 200k.
I was of the impression (and, tbh, am still under the suspicion..) that any myocarditis risk was "noise" -- not noticeably higher than that in the larger population, or that reported cases have confounding factors that would suggest the vaccine is not the cause.
That being said, I think the more interesting question is what constitutes non-trivial medical risk. 1 in 10k is really small, especially for a medical treatment.