I completely agree with the point that banning/censoring people is necessary in order to operate any internet forum. But I know from firsthand experience that bans are used to stifle valuable discussion both on major subreddits and niche ones. I've seen it happen to me and to others.
For example, on an r/news post a few years ago about the Israeli/Palestinian conflict, I replied to another comment where my content was basically the following: "If someone threatened to bomb your house, and they had a history of bombing houses, would you respond? What about after they destroyed your house?". That's almost exactly the wording I used (wish the comment hadn't been deleted so I could repost it exactly). This not only got me permanently banned from r/news, but also reported to the admins who censored the account. I suspect I pissed off a reddit admin or power user who followed me around reporting me, as shortly afterwards in a niche sub, I made another post discussing the continuum of force when it came to violent crime, quickly received several reports, and my account was permabanned from reddit. Note that both the content and tone of my posts there were similar to how I post on HN, which I think is generally appropriate.
This sequence of events bothered me a lot, because I think discussion of the use of force continuum and the ethics of preemptive or retributive force are highly relevant to today's world, and that the places where I continued (didn't start) discussion of them were the appropriate places for them. If this conversation can't happen on reddit, which it appears it can't, then we need another forum. It is clear to me today that reddit has hit it's eternal september. I can't bring myself to respond to the multitude of low effort posts that typically bombard you when you post something other than memeing.