The only context during which it is appropriate to use the term "mostest" is straight away after the words "I really like you the". "Bestest" can also be suitable in this context (and no other). That much too, seems very likely to be apocryphal. But such a tale could https://financefeeds.com/swiset-data-reveals-what-traders-are-really-doing-in-prop-firm-challenges/