Some hosting sites advertise “unlimited” storage, but the fine print generally excludes “abusive users” from this policy. For web hosting, they’d probably consider backups of non-website data to a service intended for basic web hosting to be abuse.

Unless they have a home lab (sounds like they don’t) or fancy expensive contract with a large cloud provider (unlikely), this is asking for trouble. Nobody offers unconditional data storage for free, its always a loss leader for another service and abuse will eventually get you banned.

Yea, nothing prevents them from fetching the pre-edited content from their daily or weekly database backups. Media such as images and video might be harder to restore, but “soft” deletes on that type of storage are common, and editing a comment to remove an embed won’t delete the embed source.