texpire deleting more articles than it should

I use leafnode both to read groups, and to archive groups (and it's awesome
for doing both).  I even use local groups to archive mailing list traffic so
that it doesn't fill up my IMAP box.

However, the other day I ran texpire and saw this:

   texpire 2.0.0.alpha20110815a.luascript: check mtime only
   wg21.c++.news: 8 articles deleted, 170 kept
   wg21.c++.lib: 1839 articles deleted, 16232 kept
   wg21.c++.ext: 1608 articles deleted, 4314 kept
   wg21.c++.date-lib: 0 articles deleted, 202 kept
   wg21.c++.core: 412 articles deleted, 9203 kept
   wg21.c++.compat: 11 articles deleted, 411 kept
   wg21.c++.all: 3 articles deleted, 922 kept

But I have these relevant settings in my config:

   expire = 36500
   groupexpire = wg21.* -1

As far as I understand, texpire should just be leaving these groups alone,
right?

Luckily I had the groups in question under Git, so I resurrected the articles
easily, but I had to use this invocation to trick texpire into rebuilding my
message.id without deleting those articles again:

   texpire -vvv -f -r comp.std.c++

What can I do to fully stop texpire from deleting anything, ever, except for
specific groups that I want to expire?

Thanks,
  John