I think we have a decent idea about what the dark secrets would be and what David is at the very least willing to ignore. Brandon dating someone under 18, Todd dating a 19 year old, Jason trying to kiss Tana when she was still a teenager iirc and the Dom accusations. It’s not a stretch to say that the dark secrets would be underage girls and legal but gross age differences. Throw in the drug use from the heavy partying days and who knows what they got up to during peak train wreck.
There’s also an element of exploitation with Vardan being a kid and, imo, they shouldn’t be exposed to social media like he is. One could argue that people with substance abuse problems got exploited and David definitely liked poking the Trisha (pos but mental illness) bear.
Anyway, I don’t think it’s much of a mystery. I bet David’s negatives get smoothed out a lot as well. The OCD, moodiness, an obsession with getting content, etc.