It's a lot better than Mastodon, where you simply lose everything.

The author totally glosses over that and scoffs at it being a real problem both in the thread linked and here in the comments, yet real people have experienced the extraordinary pain of watching their accounts evaporate overnight because of some capricious server admin. It's a total nonstarter for ever using Mastodon.

You'll store it on your own device, or on another service. I don't understand this criticism; where else do people back up their data?

People might be imagining it as something tightly coupled with the application rather than a data file you can just backup anywhere. Could be worth chucking a "store your profile on your own device, Apple iCloud, Dropbox, Google Drive, or your preferred file storage solution" somewhere.

To avoid repeating myself, see this comment: https://news.ycombinator.com/item?id=35885373

Note that Mastodon is even worse. Backup/restore has been generally ignored in social media.

Mastodon is definitely bad. I had to do an emergency migration to a new instance and lost all of my posts.

Calckey is working on account migration and backup that does transfer posts to the new server.

Having access to your data on your own devices is... bad now?

The issue is not "access" to your data. You're not forbidden from accessing your data in any case. The real issue is that it may be bad to have full and sole responsibility for maintaining backups of your social media data.

1) If you add image files and especially video files to the mix, the size of your data can get huge.

2) Smartphone users especially don't have a ton of free storage space.

3) In general, people aren't great at maintaining their own backups.

The question is why a so-called distributed network can't maintain distributed copies of user data, rather than forcing the burden onto the users.