Both of these violate netiquette!
As a reminder, proper netiquette is to necropost instead of creating a duplicate thread.
And shadow banning is not a tool that most moderators should even have, and should only be used against the most horrible trolls!
There's obviously a line to draw somewhere. You don't want 50 posts on the same topic clogging the top of the feed, but zombie threads where the first 90% is out of date or irrelevant are also bad. Locking a thread after it has been idle for a week or two seems like a reasonable compromise to me.
Good forum software makes it less of a sin, but that's pretty rare on the Internet. This isn't the Usenet where people's clients could be fully featured on every topic.
BTW, I prefer decentralized protocols like Usenet, there are plenty of features that would be unthinkable to leave out of "modern" clients, this could be one of them !
My observation is the worst aspect of monetization is on the communities themselves. For the first half, say, it was standard spectrum: some trolls and schmucks but for the most part regular folks with something to say. April Fools projects from the admins wowed us year after year at the creativity and cordiality.
Then came the ads and the apps, no picnic but down in the subs was a new problem: site policy. At some point, subs and posts were getting yanked or even altered by admins. Censorship, astroturfing, shilling, kowtowing to foreign investors, the whole political manipulation thing: you couldn't trust anybody's motivations anymore in a conversation. Most lately, the standard disney/youtube-ification has started.
I'm almost done, too.