§42 UrhG (
https://www.gesetze-im-internet.de/urhg/__42.html, english translation
https://www.gesetze-im-internet.de/englisch_urhg/englisch_ur...) is probably core to what an author can do about their personality rights in relation to their works:
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Section 42
Right of revocation for changed conviction
(1) The author may revoke a right of use vis-à-vis the rightholder if the work no longer reflects his conviction and he can therefore no longer be expected to agree to the exploitation of the work. The author’s successor in title (section 30) may exercise the right of revocation only if he can prove that the author would have been entitled to exercise this right prior to his death and that he was prevented from exercising the right or provided for its exercise by testamentary disposition.
(2) The right of revocation may not be waived in advance. Its exercise may not be precluded.
... (more stuff that is about compensation and how you can't use this clause to just start to exploit the works on your own after taking it out of circulation, but not relevant here) ...
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Putting stuff into the public domain would either mean:
- that an author waives their right to revocation in advance (that "rightholder" would be the public, I guess), but that's explicitly forbidden by (2) or
- that they can claw back the work from the public domain, which keeps the work in some weird state where it's PD-unless-the-author-objects.
The only way to put a work into something that is somewhat similar to the public domain under German copyright (without dying and waiting for 70 years) is to publish it anonymously with a dedication to the public, so that redistribution etc is clear, and then remove all traces that you authored it (e.g. drafts, notes, ...) - and even then it falls back to you if somebody starts digging and finds proof of authorship (§66 (2) https://www.gesetze-im-internet.de/urhg/__66.html, english translation https://www.gesetze-im-internet.de/englisch_urhg/englisch_ur...). Any legal conscious redistributor wouldn't touch something like that with a 10 foot pole.
Just use CC0, it's cleaner.
As for
> Why do we think it can't be abandoned, again like any other property?
You can't sell yourself into slavery. That's the category personality rights operate in. Does it make sense for copyrights? ¯\_(ツ)_/¯