Where was it stated that private chat was exempted from the rules?
So you know, guards and mentors are NOT able to see private chats unless a player complains. Hence, if you swore in private and were silenced then one of the people you were conversing with apparently did not appreciate the language used and decided to send a complaint, as such a moderator responded.
Also, unless a moderator is present in the location while a chat violation occurs the only way for them to address it would be for someone to send a complaint.
If you have a complaint against a mentor, post
HERE
In the "Guard Assistance" section of the forum, there should also be a thread for
Complaints About Wrong Curse Of Silence