So, if we get an email, with a message-id in the references list thatWouldn't this be an ordinary result with a cross-posted reply? Cross-posting ought to be more commonly forwarded messages than replies, but _users do the darndest things_ (to paraphrase Art Linkletter). I've often bcc'd a group reply to a friend, but probably not too often to another group or list.
We put a 'placeholder' message in the database that corresponds to thisWhy? Just to prevent the rare case of a message number being out of order in the thread? Or are the threads actually sorted by message number and its the message that would be presented out of order?
What happened in this case is that Shal replied to an email in aOther way around. The reply was to a message in owlperch. But the reply got cross-posted somehow into beta. It is beta which would never have seen the ID in that reply's References (and In-Reply-To).
The weird thing is that Brenda claims that her reply to me was made through owlperch, yet posted to beta. There's absolutely no mention of beta, nor ID of any beta messages, in the header fields of my cross-posted reply. That's too weird, I have to assume that Brenda was mistaken, and she actually replied in the Beta group, but thought it was owlperch because the subject tag said [owlperch].