Replying to a mantis ticket should add it as a note to that issue, as well as email the originator. This should maybe be configurable, maybe on a per project, user or issue basis.

Right now users can reply to a mantis ticket and it can redirect the email to other mantis users. However, a lot of useful info is emailed back and forth that should be entered as notes for that issue.

Replying to an email and copying that email as a issue note is an annoying duplication of effort.
Using the mantis feature 'send reminder' is not as user friendly or quick as just replying to an email.

There is a project in Sourceforge called mantishelp, written in php, that lists a similar feature in its main description, so I know this is possible to do in php.