Harassment, especially sexual in nature, will not be tolerated In Character or Out of Character. If someone doesn't want to interact with you that's their right. They don't have to give a reason. If they tell you to leave them alone, then leave them alone.* Period.
Obviously, this means you have the right to walk away from someone you don't feel comfortable role-playing with. This doesn't give you the right to grief or harass that person in return. Remember the first rule - use common sense.
Unwelcome out of character sexual advances, sexual jokes, or general stalking behavior through tells, pm's or on IRC will get you banned, not only from the server, but from forums, IRC, and anything else Hala related. It will also get your name put up for consideration for a CoPaP wide ban. This isn't an issue of player griefing, its an issue of safety.
Unwelcome in character sexual advances, sexual jokes, or stalking behavior is not acceptable either. If you make an advance and the character tells your character "No, I'm not interested" that doesn't mean come back later and get touchy-feely. Don't press the issue. We all have different comfort levels when it comes to RPing sexuality and that should be respected. Furthermore, we all have different comfort levels in RPing with different people. Just because a person cybers with one person, doesn't mean they are willing to cyber with you. That should also be respected.
Finally, if you find yourself in a situation where you feel harassed, first make sure you tell the person in no uncertain terms to stop. "No," "Go away," and even "F*** Off jerk" all work nicely. Its not harassment if the other person doesn't know the behavior is unwelcome. Also, keep logs and screen shots. Its far easier for the team to deal with a person when we have solid evidence they are doing something wrong.
*unless you are telling a team member to leave you alone while being questioned over a rule breaking. that isn't harrassment.