But by responding and admonishing that the person has violated the thread rules, it's also not wrong, even though the OP can delete when deemed not to comply with the rules.
I don't think it's necessary because if the OP deletes post that break the rules, then the response post after that must also be deleted because it's no longer relevant. But of course it depend on how the OP moderated this thread although so far I think moderators will delete anyone's post that quote your deleted post.
Countdowns that don't meet the requirements need to be responded to and rebuked as learning or reminding users who don't read the rules in Op. Indirectly they already know the location of the error and prevent the assumption of favoritism or only certain users get merit assistance here.
Of course Op has his own policy in moderating this thread to make it cleaner from spammers who are lazy to read the rules. I think it is necessary to leave some inappropriate countdowns as examples for other users so that the same error does not continue in the future.