gruber didn't "invent" markdown.

he took the idea from dean allen, who had created "textile" (which was featured in the movabletype blogging-system gruber used).

gruber reworked that idea slightly, then released it with a catchy name, and somehow received all the credit.

as for gruber's blog, i would say it is evenhanded and informative, albeit focused on apple and its products. the blog is certainly not "fawning", and i think most apple-buyers feel no need to "justify" their purchases.