I hear these justifications a lot, but the conclusion doesn't follow from the premises.

The value of the archival data that can be affected by deleting or editing is almost entirely only user-accessed value. Reddit isn't harmed at all from the edits. It primarily needs active regular users to improve its stock value. Alternatively, it can sell archival data for AI training.

Editing old comments removes neither value source from Reddit. You moved away from it so deprived it of both the material value of new comments and the statistical value of being an active user. Reddit also assuredly has saved data from before the API issue and can likely spot and clean the mass edits to sell the data from training purposes.

Conversely, the value to users and society is high. So many solutions to problems that are gone forever. The Internet is decaying already and it gets harder to find useful information, and those leaving decided to just burn down a library of Alexandria.

It's their - and your - right, sure. They're by definition done on comments the user owns. But this is just punching desperate Internet users in the face hoping it gives Reddit a bloody nose.