Threading corrupted (negative article numbers)

[Stephen Berman <Stephen.Berman@gmx.net>]

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Something I've never experienced with Gnus happened while reading the
newsgroup gmane.linux.suse.general: the threading suddenly fragmented
and one article appeared three times, once dangling before its thread
and twice within the thread.  When it happened I had most likely just
typed RET or `n' to read the next unread article, though I don't
remember if this was on the article that became dangling.  Here is a
screenshot of the fragmented threading:


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The underscored line is the dangling article.  The three articles
immediately below this have negative numbers; here is a schematic
showing the article numbers:

a. (  23) M Harris: 215508
b. (  46) M Harris: -3
c. (  51) G T Smith: -2
d. (  23) M Harris: -1
e. (  23) M Harris: 215508

Line a is the dangling article, lines d and e are its other
occurrences.  When I again typed RET or `n' on line a, nothing
happened.  When I typed RET or `n' on line e, the cursor jumped to
line a.

After doing this I quit the group with `Q' and then reentered it
again.  Now the threading was no longer fragmented, but different:


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There was no longer a dangling article but still articles with
negative numbers, but now only two:

a. (  46) M Harris: -2
b. (  51) G T Smith: -1
c. (  23) M Harris: 215508

Can anyone make sense of what I've observed here?  This is with Gnus
from CVS Emacs (GNU Emacs 22.1.50.1 (i686-pc-linux-gnu, GTK+ Version
2.10.6) of 2007-04-30).

Steve Berman