*scratch* buffer modeline wrong after exit

[Karl Kleinpaste <karl@jprc.com>]

I'm sending this note on Lars' request/suggestion, after a `C-c C-b'
bug report of mine proved not to be reliably reproducible.

In q0.15 and q0.16, I am irregularly encountering the bizarre effect
that, upon exit from Gnus, my modeline looks like this:

--** [gnus glyph] *scratch* [0] {1 more}   (Lisp Interaction)-----L1--All---

Note the *Summary*-style bits that remain in a *scratch* buffer.  Note
also that the buffer claims to be modified, though attempting to
execute `undo' fails, with a complaint that no more undo info is
available.

If I start killing buffers with `C-x C-k', eventually *scratch* is
reconstituted and has a normal modeline, lacking the gnus glyph and
summary counters.

As for the circumstance which leads to this error, I am not sure
precisely what it is that does this.  I have tried:
1. Both M-x gnus and M-x gnus-no-server.
2. Exiting immediately after start.
3. Reading entirely through a couple groups until they show no unread
articles.
4. Reading partially through a group so that some unread articles
remain.
5. Sending (and not sending) replies to articles being seen.

So far, I have no reliably reproducible circumstance.  It seems to
happen (guestimating) about 1-in-5 exits from Gnus.

Is anyone else seeing this in the most recent release or two?

My configuration:
XEmacs 19.16 under Linux (recent RH).
I change gnus-{group,summary,tree}-line-format, but have no
customizations regarding modelines.
All my customization is in .emacs; I don't use .gnus at all.

Clues, or at least corroborating failures, would be most welcome.

--karl