Counterpoint: mods can (and have been) paid off to promote/allow posts from certain companies, while shutting down posts from competitors.
The biggest example is u/gallowboobs, but many mods of medium to large sized subreddits have reported being approached by people offering them money to use their power to influence what gets posted.
So, while on the surface of it, it looks like a subreddit is moderated by clear, transparent rules, in most cases, decisions are made by a handful of people whose interests are not clear or aligned with the community's.
I can see that I would have been much better off letting one of my startup's users, or someone who had seen our Show HN, post to reddit and get the ball rolling. That would have generated the same type of publicity, and I would have been able to jump into the comments and answer questions in the same way. Lesson learned!
How many launches of other startups not affiliated with you did you share there first? What % of your comments in the sub would you say were on threads you didn't start?
If you were more intrinsically interested in the community, you’d probably have signed up long ago and engaged with plenty of other people’s posts, like you did here here on HN!
Is there a subreddit that has an analog of 'Show HN'? Or have HN and PH basically sucked all the oxygen out of that particular room?
Each subreddit is moderated differently by completely volunteer moderators. How things are in one subreddit does not really tell you how it is in another.
In broad terms, directly engaging as a company on Reddit by creating a post is generally frowned upon. What works better is to respond to posts in the comments hwhere your company would be relevant. But it is very hard to toe the line between spamming advertisements, and engaging with the community. 90% of companies I see trying to engage on Reddit seem to do it with metrics such as ROI or engagement in mind, rather than simply trying to make a community a better place.
If you go by the former, you'll have your posts removed and maybe even banned from the community. If you do the latter, then you will make some headway.
E.g. Do not promote your business selling router bits, DO make a lengthy post explaining the differences between router bits and how to choose one that's right for you.