Not sure what the point of "Mastodon's" opinion is? Firstly, Mastodon is pretty big and decentralised, and it has no-one who really speaks on behalf of all its users. Lemmy is not a privacy central network like a direct messenger service. It never claimed to be privacy centric as far as I know. The point is to share posts in communities, and the more that see them, the better.
But it is federated which means posts do get shared to other servers everywhere, and deleting those is not as easy as for a centralised server. Whatever I post on any sharing type service, I consider to be public.
I don't even understand why the OP calls this "Mastodon's" opinion. The link doesn't go to Mastodon. I think the parent post is being a bit of a troll honestly :( The criticisms at the link don't make sense, the person posting the link doesn't seem to think the criticisms are good, and they attribute the criticism to Mastodon while posting "Raddle". It's like they're only doing this to get everybody riled up
Mastodon is where the link to the raddle article appeared. The post on Mastodon basically said they wouldn't use Lemmy because of what the article stated.
Here is the title of the Raddle post that was linked: "Warning: Lemmy doesn't care about your privacy, everything is tracked and stored forever, even if you delete it".
But wouldn't Mastodon instances be able to automatically backup posts, comments, edits, and deletions? Hell, users would be able to do it too yeah?
The whole idea of this being a privacy issue kind of goes against the whole internet archival movement and is really a moot point.
I can see this maybe being a problem with privacy regulations though.