Can I change my username?

No. Your username is set at the time you create the account.

You can change what is seen on your posts and comments though:

• Login to your blog, go to Users > Profile
• Enter a new Nickname
• Click “Update Profile”
• Now look at the “Display name publicly as:” and choose the new name
• Click “Update Profile”

Note: All the blogs on one account use the same display name.