A feature to select a mail-thread to be auto-archived automatically. This will not affect other mail-threads among the same users of the distribution list.
Use case 1: Large DL is used for different topics with high volume of replies. Topics that are not of importance can be auto-archived to prevent cluttering of your inbox.
Use case 2: Next to auto-archive function a thumbs up can be added. This way the DL knows if the topic is useful or not and is worthwhile to eloborate even more in a follow-up discussion.