How do I change my account name?
Go to your profile on the main site and click on the "edit" link.
The first field is the display name. Change that from "trystero" to what ever you like. I don't know whether just deleting what's there will work - that is you don't have to set up a name but once you have you might have to always have a name.
This will get propagated to the meta site.
You can then copy that information to all other sites by going to you "accounts" tab and clicking the "Copy Code Review Profile to Related Accounts".
This will update everything apart from the OpenIDs you use on each site.