1) The top 50 guilds by total achievement points make the list.
2) Only the top 500 characters in each guild that have played in the last 7 days are...
Yes, your character will only be able to become a standard character at that point, but you'll lose nothing (no level loss, badge/title loss, etc.)....
We'll keep this in mind for future jewels, but I can't justify changing it after players have acquired them. You said it yourself, if you don't want...
I'm kinda torn here because I want to keep a reason for you to visit towns, but I can see where it might be nice to have a leaderboard in your house...