You are misinformed, the user didnt edit those 21 posts when told the references needed to be cited on January 5, the user only did so after the posts were revealed in our reports, almost a month after.

Particularly, when that person from then on respects the rules?

Even if the person would be respecting the rules now(which you cannot assert with confidence), given that it was proven the user lied about the artwork mentioned in the post not being made from a reference image it is well established that the user intentionally omitted to mention it not because of inadvertance but with the intent to deceive. Hence, even if the user would be following the rules now, that fact has no merit or virtue and it is in no way redeeming for there is no merit or virtue in correcting something when forced to.