It seems that my own preferences for public online discussion---usenet
over blogs over Twitter---is rather the reverse of the popularity of
those media. As such, I recently joined Twitter to publicize what I see
as a serious problem with arXiv. To some extent, I'm blowing my own
horn, but the problem is much bigger than my problem, and others who are
affected are probably more heavily affected and moreover are afraid to
speak out because of fear of getting banned by arXiv (which is itself a
problem).

Although I'm happy to answer questions here, I've probably said all I
need to say in a guest post on John Baez's Azimuth blog:
https://johncarlosbaez.wordpress.com/2022/02/04/submission-to-arxiv/ so
check that out and follow the links in that post and in the comments.
There is also a link to Twitter. I'm new at Twitter so no expert. Try
to find relevant posts---recent ones by myself, John Baez, Steinn
Sigurdsson, and Toby Bartels for a start---and like and retweet
(preferably with some substantial comment) the good ones as much as you
can. That shouldn't be the way the world works, but it is. As for
Sigurdsson's tweets, please point out their shortcomings.

So far, it seems that everyone is defending me and no-one is defending
arXiv. arXiv's strategy seems to be to suggest that my problem is
something of a one-off, when in fact it is more widespread. I would be
happy to hear from people similarly affected (and will keep it
confidential unless you explicitly say that I can mention you). The
most important things are to gather and present evidence that many
others are affected, and publicize the problem as much as possible.
There is a hope that arXiv might be forced by public pressure to admit
their wrongdoing here.