Perhaps your email client is to blame? I'm using Apple Mail in OS X Yosemite and it responds to the Reply-To header perfectly.
My raw email:
Content-Type: text/plain; charset=UTF-8
X-Mailer: Postman SMTP v1.4 for WordPress
From: 'Bobo Fet' <postman@postman.ca>
To: Jason Hendriks <jason@postman.ca>
Reply-To: 'Bobo Fet' <bobo@starwars.com>
Subject: Test!
Date: Thu, 19 Feb 2015 17:17:44 +0000
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
MIME-Version: 1.0
Test=0A=0A--=0AThis e-mail was sent from a contact form on Coding Monkey=
(http://programmer.jasonhendriks.com)