I use filtering to tag email tasks as "In Progress" or "Done" etc. by parsing the body of the message. Sometimes I remove tags manually because the task is, after-all, not done, and needs further work to be done on it. The problem is: if I get any reply after that, say for a question that needs answering for the task to be complete, then it RE-TAGs the thread because of the old message body.
I would like the filtering to work on only the new content in the body of a message and ignore the old. I know that gmail creates a new body with old content, but perhaps you know what I mean. Is there a way?