Some relays will maintain it, others will not, the difference is that you don't depend only on one relay... as a user, what I should be able to do most is share my well-categorized lists of mutes (if possible, they can be displayed in a list section in the profile) and let each user decide if they want to subscribe to it or copy the npups and create his own to handle it better... basically this is what I ask for in terms of moderation issues