I think it will be resolved case by case by moderators. I've read it dozens of times so that it becomes a provision where 1 mistake made by a forum contributor in the past (unintentional, or for other reasonable reasons) can still be considered by the moderator not to ban it. You can't say the rules should same apply to all forum users, although I will not support plagiarism but the moderator's gentle attitude to forum contributors is highly expected. Losing one useful contributor to a forum with 1 error is not worth the hundreds of spammers there are.