Quoting a rule from the unofficial list of official Bitcointalk rules:
22. Advertising (this includes mining pools, gambling services, exchanges, shops, etc.) in others threads' is no longer allowed, including, but not limited to, in altcoin announcement threads.
In the past, I had made a reply to a thread talking about a criminal who got caught using mixers. I remember that I had linked MyCryptoMixer and that's possibly why it got removed.
Now I ask: Shouldn't we define what's an advertisement? There are tons of posts about ChipMixer (and some for BestChange) scattered through the forum, but haven't got removed and I'm mainly curious in what extent should I be careful when I'm writing regarding a product.
Based on my experience, linking to a product means advertisement and the post will get removed, but talking about it means that it's fine. Well, that's a false thought in my judgment; if you disagree, do it argumentatively.