I've replaced the old kin system with a new one. It still needs some improvement, but I think this one is a lot sounder. Here's what's new:
You can choose to memorize a player without making him kin. Memorizing does not require the consent of the other player, and does not reveal any information about him, but you do get an entry in your kin list, which you can give a nickname (the nickname always starts out as "???"). Apart from nicknames, memorized characters can also be categorized into groups (you can pick from a selection of 8 different groups, represented as different colors).
Whenever you see a character in the game view that you have previously memorized, his name will float above his head for a while and slowly fade out (in the color if the group you've put him in). If you want to see it again, just hover your mouse on him.
Making a character kin can be done once you have memorized him. Kin relations, unlike memorization, is always symmetric (either both of you are kin with each other, or none of you are), and requires the consent of the other part. Functionality gained by making people kin still includes the ability to start chats and invite them into parties remotely.
Obvious functionality still missing include the ability to select claim permissions by group, and making the PM chat tabs display the given nickname instead of the actual character name, but this should still be a lot better than previously.
Enjoy!