[rt-users] Status changed from Resolved to Open during reply?

[Kent]

Via the web interface for RT 3.2.1 clicking on Reply to a ticket that
is already closed and leaving the Status box at 'resolved (unchanged)'
the ticket will reopen itself after the update.

Any way to stop this behaviour?
I want the ticket to re-open itself if a requester sends in an email
but not if one of our staff is replying to an already resolved ticket.
Am I missing something obvious here?

System is RT 3.2.1
Solaris 9
Apache 1.3.31 w/FastCGI

Thanks.