I have an interesting take on this that makes me agree with Sir Draklar. I once created a thief character for the purpose of giving good folks something to bounce their RP off. He was not an evil man. In fact, the way I played him, he was very likable, always smiling, and treated everyone with great respect. That is how I made his In character description.
However, behind those smiles, he would cut your purse in a blink, and be on his way. This was also done without any ill intent on his part. In his mind, he was doing folks a favor by teaching them the value of their things. This is how I gave this info to people in the character description -after- the IC info:
THIS IS OOC INFORMATION YOUR CHARACTER WILL NOT KNOW.
-This character is a thief. He is very good at his trade, and has never been caught. He is also new to this city. He may approach you in /tell if you are deemed a good target. It is your choice to take part in the RP. If not, he will decide you are not a good target after all.
I RPed with him for about a day, and did go through with a few pickpockets. Most people turned out to be 'not a good target after all'. One however, who up to that point I had considered a good roleplayer, took one look at me and turned to his friend with a sour look. "Watch out for that one. He is a thief."
I immediately sent him a tell asking how, exactly, he knew this. He responded that his character had seen me around through the years, and had noticed things vanishing. I re-informed him that my character had just came into this city, so he would not have seen him before. The response to that still gives me cringes. "I am a 1000 year old elf, and I have been everywhere." Instead of arguing an entirely pointless argument with the fool, I smiled and walked away. In retrospect, I should have asked him how the trip through the Portal was.
Lesson learned: If you want to keep a secret, keep it secret. Test successful. This lead to keeping almost -all- of the info in my RPs secret from everyone, even those helping in them.
I suggest you do the same.
Bonus riddle: “If you have it, you want to share it. If your share it, you haven’t got it.”
edit: Also, a great many people have noticed (and sometimes figure out my secret characters) by my use of double brackets to be sure some thick head knows it is OOC for sure. [[yey for OOC]]