Low moderation and high level discussion is very possible and very common, but it depends on the topic and maybe the language. Just yesterday I've been on a French language forum on gardening, and this kid of dedicated community do not seem to struggle to keep away trolls and memes. Must be much harder for an English language forum on mangas, or a French language forum on politics. I'm not sure about Reddit, the subs I visit are either monocultural and barely interesting, or full of trolls and memes.