address filters for mailing lists

I’ve often had the need to address only a subset of people on a mailing list. For example, the devel mailing list of an open source project can have many independent subprojects, so why not allow Gmail-esque “” filters, where the LABEL can be any word to indicate subset information. Then, people can specify to the mailing list to either allow only emails with that LABEL word(or a set of terms), or to ignore emails with that term. So all you would need to do is reply to the mail whose label you want to ignore by appending a “SYSTEM:IGNORE” to the subject or something like that.

It would be really cool if someone can come up with a nice way to fit this into mailman or some other MLM as a proof of concept. The ignore emails with this label command is quite feasible and user friendly, IMHO.