In My Humble Opinion, means that the message may sound opinionated, but the sender realizes that everyone may not agree with him. Just In Fun, means that the recipients should not take the message too literally. Many smilies are used simply for fun, and you can find smilie dictionaries on-line. Netiquette may seem like simply a list of suggestions about good manners, but it has the force of law among those people who know what they're doing. Moreover netiquette can be and is enforced.
Someone has to take responsibility for setting up and maintaining a discussion list.
When a person joins a discussion list, he becomes the guest of the listowner and should behave accordingly. The listowner may delete anyone from the list for whatever reason, and there is no appeal from a listowner's decision. He may give a short lecture on etiquette, or anything else he wishes. One should always pay close attention to administrivia, since most listowners try to be as unobtrusive as possible. Some succeed so well that listmembers may forget that there is a listowner and set and enforce their own standards of conduct.