Something bad seems to have happened to scoring

[Karl Kleinpaste <karl@charcoal.com>]

My score rules are behaving differently than they ought, or used to,
not that long ago.

I'm looking at my own outgoing archive of Usenet-posted messages.  A
message is marked `Y' and italicized (scored down).  I wonder about
this, and mumble `V t', which gives me a *Score Trace* buffer showing:

("vanillaknot.com>" 10 nil s)  ->  /home/karl/News/all/SCORE
("cinnamon.vanillaknot\\|mesquite.charcoal" -10 nil r)  ->  /home/karl/News/usenet/SCORE
("kleinpaste" 10000 nil s)  ->  /home/karl/News/all/SCORE
("kleinpaste" -10000 nil s)  ->  /home/karl/News/usenet/SCORE

Short summary of triggered score rules:
- I score up on things that are followups to myself, globally, and
  this article was one in a longish discussion chain.
- But I cancel that in my "usenet" group.
- I score up myself globally, so I can easily find my own messages,
  and so that threads in which I'm participating sort to the top..
- Again, I cancel that in my "usenet" group.

Hm, it ought to be score zero.  But `V S' says "-10".

In a similar vein, I'm looking at articles in list.ding:  

O   28-Jan > [   6: Harry Putnam           ] Was I dreaming...?
R   28-Jan +---> [   7: -> ding@gnus.org       ] 
R + 28-Jan |   `---> [  10: Josh Huber             ] 
R   28-Jan |       `---> [  21: Harry Putnam           ] 
R   28-Jan |           `---> [  13: ShengHuo ZHU           ] 
O   28-Jan |               `---> [  14: Josh Huber             ] 

Josh's article, following up to mine, scores up, based on References
mentioning me.  But Harry's, ShengHuo's, and Josh's 2nd are not; `V S'
on each says "0", yet the `V t' *Score Trace* says:

("vanillaknot.com>" 10 nil s)  ->  /home/karl/News/all/SCORE

So it clearly ought to have score 10.

What gives?