>In particular, placing limits on abusive content and users would make the site more attractive to advertisers.
I see no problem with this. I purposely avoid recommending or even mentioning reddit to the people in my life because of all the horrible content on the site. I won't promote these subs, but there are many, many popular racist subs and subs that promote violence against women and, hell, one that is dedicated to showing photos of dead women who were attractive in life. There's a creeper sub that shows candid photos of women on the street that pathetically skirts the rules by pretending its about "fashion."
My god, reddit is a mess. I can't ever imagine recommending advertising there. I can imagine videos games, e-cigs, energy drinks, etc advertising there as these things already have a lousy reputation, but reddit is not on the path of being this broad forum with lots of members with disposable income. Growth isn't impressive when its just more of the same, largely unprofitable, "manboy" demographic.
This is why USENET lasted so long and was so prolific amongst techies. It never had to make a profit. You could trivially start new "communities", etc. Reddit is pretty much USENET as web, but the problem is, someone has to pay for all those servers and staff. No one is donating or proving access as part of your shell account like they did back in the USENET days. I find it questionable that such forums would ever be profitable. I suspect the next gen reddit will be something that has more in common with torrent-like tech than old school client-server web tech.