Stripping quoted text from emailed ticket replies

Hello all,
The other major problem my boss has with RT is how emailed replies include
quoted text/original messages. If four replies come in, each carrying with
it the entire conversation history, the web UI showing the ticket very
quickly becomes a huge mess. I found a thread from this list that says this
feature was released in 4.0, but I don’t see the option anywhere.
http://www.gossamer-threads.com/lists/rt/users/98679

If it’s an option, how would I turn it on? If there’s a way to have some
cut-off text, like “–reply above this line”, below which all text is
simply discarded, that would be great too. I’m on 4.2.8, so maybe the
feature just got delayed and wound up in a newer version than I have?
Thanks.

Alex Hall
Automatic Distributors, IT department
ahall@autodist.com