It's not a community setting or feature. It's a fact of the internet.
If you publish something to someone else's website, you no longer have any control over it. And federation means publishing your content on thousands of websites, many of them not even running the same software. Your comments are out there on mbin sites, Friendica sites, Hubzilla sites, Mastodon sites, Misskey sites, and many others. Someone's pribably got a custom web server they developed, slapped some ActivityPub inside of it, and didn't bother to make it even understand delete requests.
This is the internet. It is public, and it is forever. You really need to treat it as such.
There are multiple publicly accessible food databases out there. Waistline uses Open Food Facts and the USDA food database, for instance.