Thanks, everyone. I have heard from a few individual craftspeople or artists who post about their professional life here and get hassled because that's "not allowed on the Fediverse".
If someone is harassing or abusing people, shut them down, by all means. And if someone is breaking your server's rules about commercial activity, report them to your moderators, of course.
If you have a fediverse account, you can quote this note from your own instance. Search https://cosocial.ca/users/evan/statuses/114485839951193654 on your instance and quote it. (Note that quoting is not supported in Mastodon.)