The works in which copyright can subsist are typically divided into two sub-classes. Works in the first sub-class are known as authorial works:
Original literary works;
Original dramatic works;
Original musical works; and
Original artistic works.
For copyright to subsist in these works, the work itself must be ‘original’. This is traditionally seen as requiring that the author exercised skill, labour and judgment in its production. Three of these works are also subject to a fixation requirement: a literary, dramatic, or musical work must be recorded. It is immaterial if this was done without the author’s permission.
The second sub-class of works in which copyright subsist are often known as neighbouring or entrepreneurial works:
Typographical arrangements of published editions.
If anyone says “well, toots are none of those…” I’ve seen people posting original short films and pieces of music, I’ve seen people write fiction that fits the medium of the toot (sometimes one toot, sometimes a thread), and obviously a lot of people on Mastodon post their original art.
Edit: Just realised you might have meant data protection laws. Here’s the UK one - turns out that the scope is limited and I can’t tell whether it applies to social media posts? It’s defined as “any data that can be used to identify a living individual. … Individuals can be identified by various means including their name and address, telephone number or email address.”
I am identifiable by my toots in many ways - I talk about things that make me very easy to find online even if my name were removed. I’m not lawyer enough to say for sure whether it’s covered by the DPA.
In any case, if you are allowed to manually delete all your toots one by one before you close your account it makes sense to provide a way to automate that!
Edit: Even if the law weren’t on my side, my point still stands:
Mastodon is all free and open source, and a big chunk of that is about control over one’s data, no? I don’t think Mastodon should keep our toots if we want to delete them. If people want their toots to outlive them, they can just post saying “this account is no longer active” and stop using the account.