By default the CCleaner blocks the keywords "anal" and "rape". The following message was blocked from trade due to the "rape" keyword:

WTS [Drape of the Forgotton Souls]

Technically, working as intended.

Blocking legitimate messages can't really be the "intended" way for it to work. Any chance it can somehow detect if keyword is part of an item string and ignore it in that case?

That would create problems with people purposely wanting to filter out items, such as thunderfury :/

Hmm fair point. I guess there is no solution that will satisfy all criterias. I'll just remove the rape keyword.

Eventually I want to have keywords set on a per channel basis, maybe that will satisfy.