I think some people associate the word marketing with lies, scams, and whatnot. What if we view the word marketing as a way to market products in a more neutral sense.
Can his honesty a marketing material? why not? it depends who reads it.
A message can be a marketing material regardless the intention behind it.
> The difference between DHH and others is that he's actually practicing what he preaches more often than not.
I think we all know that otherwise we'll call people who don't practice what they preach as a not-genuine.
> They actually believe this stuff and don't mind sharing what they think.
Most people believe on what they build/working on, otherwise it's a one-trick pony and it takes a lot of guts to work in such place especially for engineers.