Look, you can make all the rules you want but in the end vibe check is the only way to have any sort of quality.
Look at Reddit… abundance of rules do not save that place at all. It’s all about curating what kind of people your site attracts. Reddit of course is a business so they don’t care about anything other than max number of ad views.
Small non profit forums should consciously design a site to deter group(s) of people that they do not want.
I feel like you are being a bit contradictory: the suggestion is to dissuade AI content - isn't that "design[ing] a site to deter group(s) of people that they don't want"? I personally don't want to vibe check every HN comment if I can avoid it, I don't even think you can quantify that in any meaningful way. We can engender a site like that at least in spirit. It may be equally as difficult but it's still worth fighting for.
It's not about the rules. It is about intent. The rules are just there to alert newcomers and repeat offenders to the fact that they are in fact not operating according to the rules. That way there is something to point to. Then they can go 'oh, I didn't know that, sorry', and then it is all fine or they can do an 'orf'[1] and persist and then you throw them right out.
[1] https://news.ycombinator.com/item?id=47321736