This is what discussion threads are there for. If users want non content related updates about a creator they can watch the discussion thread.
We're already doing that, but not every model has a discussion thread yet and due to the server transfer all sticky posts were unsticked and are somewhere in the thread now. If you see a link to a discussion thread in a content thread or create a discussion thread and post the link in a content thread please report that post and ask for it to get pinned to the top.
That would require being able to tell when the posters are intentionally posting fakes, which is probably impossible. Most of the time it's someone being an idiot, taking things at face value and not taking 10 seconds to apply some critical thinking skills. Just report the fakes and they'll get removed.
While I understand your stance and appreciate the concern for the user, I think there should be concern for the creator as well. I think that potentially thousands of people seeing a sale is a good reason to allow it for the same reason I think people should turn ad-blockers off on websites they enjoy. We're getting free shit, and the advertisement generates revenue for the owners and operators of the free shit we enjoy, giving them more incentive and resources to create more of what we enjoy. I'll fathom a guess that less than 10% of people who watch a content thread also watch the respective discussion thread, which neuters the effectiveness. The annoyance of an occasional notification because a sale is posted is an insignificant price to pay for access to the content.