Leverage for what purpose? To fix reddit? Let reddit die or not die.
Reddit has always come after mirrors and they will easily get courts to take down the instances. Don't forget that prior to the API change they came after pushshift.
Additionally, anyone mirroring reddit on the moral basis that the content is owned by the creators and reddit is an exploitative rentseeker, has an obligation to not become a rentseeker themselves. This means things like ensuring that content that users voluntarily delete is also deleted in the mirrors. Reddit in fact had a large battle with pushshift about this years ago such that pushshift supposedly now only keeps history of moderator and admin edits. I agree with that ethically.
And in many cases you may be legally required to do this. To be clear Reddit made pushshift change to respecting user delete requests because of legal exposure and compliance risks.
Not to mention that you don't really know that anyone intends their content to be mirrored on sites they do not use. Particularly now that Reddit seems to be forcing private subreddits to be open. There's no moral high ground for doing this.
Are you certain it is the exact same comment or post? I think people are deleting everything (via scripts or whatever--some scripts are known to not work/only appear to be working--particularly ones that make use of pushshift which reddit destroyed a few months prior to this incident), but everything isn't actually everything because of the way reddit hides content in certain situations. When people have posted screenshots it has been content from subreddits that had be set private during protests and reopened. Reddit annoyingly hides your own content from yourself in many circumstances.
I'm not saying these undeletes definitely do not happen, but people have needed to delete content on Reddit for reasons the pre-date the protests. The legal risks to reddit for them to be caught restoring content that a user deliberately deleted is significant. So unless a whistleblower or compelling evidence emerges Occam's razor will go with reddit bugs and "features". Everyone knows reddit is bug-ridden.