More specifically: “4 people died from covid” is also true

AFAIK they would get the info “which user said what”. The source would be what ever instance you are from tho, not your own ip. So the owner of a instance knows as much as everyone else.

I think they meant your info being sold on dark web markets, not your behaviour on the dark web being sold.

I am not sure as well, but maybe they meant “maybe an early and public disclosure increases the urgency of the fix for the developers”?