I've thought discussion about Bitcoin mixers was prohibited on the forums?
No, the discussion of mixers is not prohibited in the forum, only any form of advertisement that could be seen as promoting a particular mixer or mixer use in general that's not allowed, at least based on what I understand from the quote below.
- Mixer URLs will be automatically wordfiltered out, but you can still discuss mixers otherwise. Using link-shorteners or other obfuscation techniques in order to post URLs which would otherwise be wordfiltered is not allowed.