When I hit reply, the sender of the message I'm replying to appears in a "to" field, but then there's a second "to" field that's left blank. Is there any way to set the default so that when I hit reply, this second "to" field does not appear?
This is a convenience. You'll find as you enter multiple recipients, the BB will continue to add another blank To field. Ditto the cc and bcc fields. Pretty neat, I think.