opposing and radically different viewpoints are welcome. Echo chambers are what kills growth.

Content does have mostly subjective qualitative assessment, yet there is also content that has objective quality to it. Utility of content is one such measure. Knowledge about certain things has utility, and has more objective value than something that doesn't. Quality is measured in people work in many areas, even in creative, writing, and other areas you might apply as subjective. There are many degrees of quality measures to apply to different contexts. It's not about an absolute measure.

You're also conflating the issue of being able to objectively determine a valuation of something, with whether that's possible at all, by your argument with Facebook and other popular content. Popularity doesn't determine objective quality. Popularity doesn't determine truth. It's just a perception of what is trending and plays on emotional preferences of the most part. 

Popularity is subjectively determined by peoples whims, wants and desires, not necessarily measured on actual meaningful quality motivations to improve their lives or the lives of others. Being led by basic emotional feel-good motivations is a non-reflective process, not a reflective, contemplative, thoughtful understanding of what to do and why to do. Populism, jumping on the bandwagon, is more in the herd group mind that individualist authentic thinking.

Anything happening is objectively happening, so yes "popularity is objective" but your conflating the issue here with what is meant. As I said, quality has subjective measure, and objective, depending on what your talking about.

Microbiology might have some utility for certain things, but there is other knowledge that is more useful in people lives if they could understand why. What is the utility of microbiology in someone's life? Will it help them improve the quality and condition of their lives on their own? Because the quality of important truths, principles and values for living, will help improve the quality and condition of our lives.

Approximately 5 Billion bibles have been sold and that makes it far and away the biggest selling book in history - http://www.guinnessworldrecords.com/world-records/best-selling-book-of-non-fiction/

Be careful which blogs you read - the author of that blog used Wikipedia as his source and we should never trust Wikipedia. The blogger pulled his data from a fiction only book sales page so the only result one could expect to receive are fictional - https://en.wikipedia.org/wiki/List_of_best-selling_books#More_than_100_million_copies

Always check your sources and trust no-one - truth!

Your perception of quality is subjective.  Not quality.  Either realistically assessed quality will bring value to the steem ecosystem, or if a subjective perception of quality deters users who disagree with the assessment then we devalue the system from the loss.

Yes, limitations to interaction need to be understood and micro communities are good. Sub tokens or sub pools for different types is an idea too.

Agree. For that, some construct like private groups or hidden friends is needed.