Wouldn’t people on that subreddit be similar to people on HN: fringe and rather ahead of the curve (relatively speaking)?

I don’t know much about urban planning but I see it in tech: the stuff discussed on HN and presented as more or less normal/best practice isn’t being done or even thought of as “best practice” outside of the HN crowd. See enterprise development and a vast number of agencies or other companies that, together, make the bulk of the software being made and sold today where basic things like unit testing or the open/closed principle are seen as a waste of time and unnecessary.