Normally, the default reply message's subject is the standard email
message threading subject, "re: <original subject>" (or,
if the original message's subject already begins with some form of "re:",
then simply "<original subject>"), e.g.
This project preference allows administrators to change the default
reply message subject.
Using the value in the above example would result in this subject:
The user typing the email reply can still change the subject.
