I'm sorry but it is implied. Don't know why anyone has not called you on this in the past but they finally have. But the Server Rules applies to everyone.
Since many people posted without seeing that 3 advisers and a DL said it was ok, I will repost my response and say this. IF FU meant F@#$ YOU, it was not directed at anyone other than maybe himself.
Each of you who said you would moderate this name need to go read:
Acronym swearing, such as wtf, lmao, fubar, bs, etc are ALLOWED. Please do not warn or take action on players using these acronyms. The exceptions are : STFU and GTFO only because it is almost always directed at someone in a disrespectful tone. As such, the warning given to the player would be to "Please respect other players."