How about a feature to privately flag individual users? I think of something that allows users to mark other users with i.e. a green, yellow or red flag. Only the user that marked the other user himself will be able to see that flag next to the username of the other user. It's not as harsh as ignoring other users, doesn't make comment references to them incomprehensible but still allows to just skip questions of certain users or to spot comments of users that might be more likely worth reading than that of others.
The problem I would like to solve with this is that many users have a username of the form user1234567 and a generic avatar which makes it difficult to recognize them. On the other hand I find it difficult to recognize the users as comment authors due to the lack of the otherwise ubiquitous avatar image.
Of course it would be also nice if one could optionally add a few words to the flag if that is feasible.