Add email header to distinguish reply emails from other emails

As discourse gets closer to its goal of becoming the wordpress for forums, I’m a member of a growing number of discourse forums and all of these are sending emails to my inbox. Most of those notification emails, I’d like to file into a separate folder right when they arrive. Most, but not all. For example, I’d like to keep replies to my posts and mentions in my Inbox.

Is there any way to identify these based on email headers? If not, we can also search the message body…

Edit: Given that there currently seems to be no answer to this question, I’m turning this into a feature request: please add an email header that specifies what kind of email this is (i.e. why discourse is sending it).