IOD: A New Type of Rule for E-mail or RSS Readers

I've joined a lot of busy discussion lists.  It turns out that 1 of every 10 (rough estimate) of the conversations are useful to me and I could care less about the rest. Typically I see people create folders for these discussion lists to remove the noise from their inbox.  If I did this I might as well unsubscribe because moving something out of my inbox means I won't get to it... ever.

Recently I created a new rule; All the messages from these discussion lists come to my inbox unless they contain "RE:". This means that I'm generally only getting the start of every conversation... sort of like reading blog posts.  Then, if I'm interested in the responses because the first poster asked a question that was relevant to me I have a marker to the conversation to get to the rest of the posts that I DO move to a separate folder.

This works, but isn't as good as I'd like. I still have to dig though all of the conversations that don't interest me to get the ones I want. It should be as simple as "Mark for Followup" that any responses to THAT message go to my inbox.  RSS aggregators also need to think through how people follow the conversations in a blog. I don't care about all of the responses to the blogs I'm subscribed to, but I should be able to mark the conversations that interest me.