I say this coming from my own experience growing a community of hardware hackers who have even less of an inclination to chat since they aren't always in front of a computer.
These things then feed off of themselves – in a sociopolitical 'guardian' type community (/r/atheism, /r/childfree, etc etc) it ends up becoming highly caustic towards the outgroup with everyone competing for in-group status points, while in a 'trader' type community (/r/entrepreneur, /r/marketing), you end up getting flooded by shysters and self-promoters.
The moderates shake their heads and leave, and you're left with the inmates running the asylum.
Only wrinkle I'd propose: The "moderates", or any of the characters you define, aren't fixed, and personal circumstance often colors which role one plays at any given time.
Continuing the reddit example. You could limit contribution by three routes:
1) Limiting the number of posts. For example, 3 posts per week, max.
2) Limiting the visibility of posts. The more you post, the less an upvote counts. Effective Upvote Value = 1 / (posts this week)
3) Limiting the visibility of posts based on post quality. The more you post in a week and the lower your per-post average karma, the less an upvote counts. Effective Upvote Value = (per-post average karma) / (posts this week)
Just a thought.
You probably weren't around for it, but HN experimented with something like this where each commenter's running average point tally for the last X posts or Y time was visible on their profile and indirectly visible on each of their comments. Their name (comment?) would appear in a different (darker?) shade the higher their running average.
I personally liked it, but it was rolled back after a couple of months. I think people became afraid to make replies that wouldn't accumulate up votes, and I know I wouldn't reply to threads if someone commented a day later because "it wasn't worth it."
Also there are communities around conventionally caustic topics (eg. Lambda: The Ultimate for programming language design, Penny Arcade for games) that manage to survive for a decade+ with no loss of quality because of moderation policies. For example, L:tU has an "avoiding ungrounded discussion" policy - every thread must be centered around discussion of a published academic paper, which first of all keeps the focus on people who actually do work, and second of all discourages everyone without the background to read and understand academic papers.
Something Awful has used this to great effect to keep trolls in line. I wonder what % of their membership revenue comes from banned users purchasing new accounts.
Neither of these is anything close to a subreddit or forum which is the "community" to which the thread is generally referring.
Pretty sure we've reached peak-discussion. Future online communities will be based primarily on activity.
Very little challenge of ideas takes place - either from within communities or from outside. The whole thing has become a Wittgensteinian language game where people compete to praise or denounce the latest political trend in the most caustic or verbose way. It's tiresome and offputting to people unwilling to subjugate their entire online persona to their identity.
Based on its usage in these last two comments, I think I must not understand what the phrase "Growth Hacker" means. I thought it was someone who was critically focused on increasing the numerator and decreasing the denominator in various SaaS KPIs. You don't seem to be using it that way. Is this a new job title in the Bay Area? Or, more generally: would you define this phrase for me?
Which isn't to say that can't be successful. With a piece of shit MVP coded by the winning bidder, some slick design, a good sales pitch and a ton of luck you might just get enough money to pay a real programmer enough to develop something that can actually get some serious investor cash which you can use to rewrite it yet again to get a real product that can scale.