Posts which are considered as spam are not related to the topic then it will be deleted when a mod see it or when someone report it.
His reply was related to the topic. He even briefly mentioned a flaw he found with the service he tested.
If that is the case then it should be sorted out, I am not sure is there any post deletion got revised after the appeal but it can be avoided in future. he mod who handled it can give better explanation for this than anyone so we can identify the actual reason behind the deletion.