For meaningful discussion, some form of top-down moderation absolutely is required. That does not mandate imitating any particular other site's manner of top-down moderation, however. So ask yourself, what about top-down moderation is harmful?
Says who? This site has meaningful discussions day in and day out, for years without any top-down moderation. I've been on two other social communities before Hubski that, while they employed different mechanics, also lacked any top down moderation and meaningful discussions were had all the time then too. They also had different social structures for handling goons. Feeling fed up with Reddit, I actually lurked this site for about two weeks before creating an account. Know what made me want to join? The meaningful discussions.
Furthermore, it's not just on the internet, but people have meaningful discussions on numerous topics day in and day out without any outside moderation. Moderation isn't what drives meaningful discussions, it's the desire for connection and belonging, the desire to both expand who we are as people while also feeling valued and validated by our peers. There is an socially created mechanism that encourages good behavior and its called manners. You don't need your mother standing over your shoulder every day to remind you of good manners.
Where things fall apart, as Reddit can be a great example sometimes, isn't by moderation or lack there of, but anonymity. Anonymity by hiding behind a screen name and anonymity of being just one voice lost in a sea of tens of thousands. When no one is gonna remember you from the next comment down the line, all of the sudden social accountability goes out the window.
If you want to create communities under the fundamental requirement, there has to be something better than following users (who won't share everything I want to read) or following tags (which offer absolutely no moderation). Think about how small communities work on Reddit - someone has an idea for a subject, they create a new subreddit, act as its (usually sole) moderator, people post/view content there.
Site mechanics are like game mechanics. Final Fantasy and Call of Duty are both video games, but they both play out completely differently. Hubski, Reddit, and Facebook are all social sites, but their mechanics also play out completely differently as well. They all have their advantages and they all have their drawbacks. Hubski is actually a pretty nifty setup, in that you can follow users, tags, and even websites, and depending on who and what you follow, your feed is influenced. Just because you follow a certain user, it doesn't mean they control all that you see. Users can't control what you do and do not see, only you can control that.
To actually produce a workable system, we need something like: every user is the moderator of their own personal subreddit on every single subject, but anyone can post in that provided they have appropriate ranking (settable per user+tag to either "whitelisted" or "not blacklisted"). Allow anyone to add tags to any posts, but the tags will only be relevant to people who (directly or indirectly) trust them for that tag - have something similar to "upvoting the fact that a tag applies". Do not make it possible to follow users, except in a specific tag (but do provide a standard tag for "follow me in this for when I start a new tag"). But do have the sense of tag relationships - perhaps a "suggestions" stream from any particular stream you're viewing.
Nifty ideas, but I think they'd have drawbacks as well. mk is always up for suggestions though. The thing is, the mechanics of moderation for this site actually compliment the structure of this site very well. At the same time, I've been here just a little under a year, just like you, and I've seen multiple occasions where mk has deliberately and publicly made changes to the site mechanics to address certain issues. Every single time he does, he always says to one affect or another “Let's see how this plays out. We can always change it.” Think about that for a second. You're using the site of a man who values his creation so much, he's not only willing to accept its imperfections, but actively polishes them out. He wants to make this site better, not for income, but so that we as users can feel welcome to stay and participate, day in and day out. If for nothing else, that type of ownership makes this a site worth being a part of.