I have a story to tell, about the demise of one of the largest internet forums in my language. About ten years ago, when smartphones just started appearing, the forum did not have a mobile version, and there are various 3rd party clients on the App Store or Android Market. Later on, one of the largest 3rd party client was blocked, because of they hammering the forum's servers too hard,. Or something about caching and…
The tech isn't the challenge with something like Reddit, even the comically inept Reddit leadership could figure it out after all. The difficult part is finding a few hundred mods willing to work for you for free, filtering all the filth that tries to be posted. Only if they have a solution for that can try going their own way.
Even $1 per month is enough to keep a lot of the outrage junkies out and you can use the revenue to pay for moderation of the smaller group of power users that remain.