The category “Abusive chat” is the title for all social infractions that fall under “abuse of the chat system”. That does not have to be offensive things. It can be anything that is inappropriate for the game and breaks the rules. It also includes advertising, spamming, trolling, etc.
Don’t get bogged down with the category into thinking it had to be abusive or offensive to be penalized.
Chances are if it really is about a posting for a group, that it was reported for spam or advertising. If a GM felt it was valid, they will apply a penalty. If not, they just close the complaint. They DO make mistakes sometimes though - hit the wrong button and vacation someone they meant to clear the complaint on.
The person who is penalized, and ONLY the person who is penalized, needs to appeal. They can appeal up until they say no more appeals on that subject will be allowed or it crosses into GM abuse territory.