I've sent this privately to avoid "polluting" the public thread.  I haven't followed this very closely, but:

1. As I understand it, this guy doesn't really understand "image" frequency reception.
2. From his last message, I think he will "continue the fight", perhaps on other forums.

So, I'd suggest a policy statement on your web site, something like:

Chirp will not accept or support modifications that may cause a radio to actually operate (including receive) on a frequency or in a mode that is different than the frequency or mode displayed.  Such modifications may cause users to operate on a frequency or in a mode that they do not intend.  Discussions on this matter are considered "off-topic" for the mailing list.

Sincerely, Dean