Shredding Users wipes out a Ticket - bug?

I have a script executed by a cron job that is intended to remove
unprivileged Users who are not Watchers from the DB.

The Shredder command it generates looks like this:

/opt/rt3/sbin/rt-shredder --force -sqldump
/opt/rt3/var/data/RT-Shredder/Users/2009-10-01-7384.sql --plugin

A recent run removed a Ticket apparently because it had earlier removed
a User who had submitted a Reply to that Ticket. The User was otherwise
not a Watcher of any Ticket. The user (i.e., the person who owned the
shredded User account) also owned the (different) account that was the
Requestor for the shredded Ticket. I.e.,

Person P submits request using email account A(EM)
RT creates Ticket T and possibly RT account A(RT)
P responds to Reply from RT using email account B(EM)
RT creates RT account B(RT)
Shredder removes B(RT) because B(RT) is not a Watcher of any Ticket
and as part of the same process
Shredder removes Ticket T (because it contains content submitted by B(RT)?)

Is this a bug? It would seem so to me.

Is there a workaround?
Gary Hall
Network Support Group
Simon Fraser University