1. RF Rules, especially rule #5. No mention of using asterisks or prohibiting it.
Because there isn't any need. The filter automatically replaces profanity with asterisks, except (as was explained to you in the post that you linked to) when someone is using voice to text, in which case the first letter is usually visible.
But when we see that we just assume someone's using voice to text and we don't ding them for it.
2. OPs and posts by staff, saying either that asterisks should or shouldn't be used.
First off, just because a staff member makes a request, the request doesn't amount to some kind of unwritten rule.
It's a request. We don't have any "unwritten rules".
Every rule is subject to interpretation of course but if we listed every possible interpretation or application pertaining to any specific rule every rule would have to be about a thousand pages long.
Second: I really doubt you've ever seen any staff member saying not to use asterix's