[pclmulqdq]

I publish them somewhere I have control, like my website, and ask archiving services to archive that page. I don't need them to be under nobody's control.

If someone compromises my blockchain keys, it's about as bad as if someone compromises my website (in terms of the actual attack vectors).

[kuramitropolis]

Unless you go full self-hosted, your website is also under the control of your hosting provider and DNS registry. You implicitly trust those, until you don't. (See the Linode/Itch.io gaffe from the other day.)

And what if your use case requires you to prove to others that you (or your publisher) can't surreptitiously and arbitrarily alter the information you published?