This is only a small annoyance, as a simple workaround exists. If you do the following:
- Go to loginpage on any SE site
- Select WordPress logo
- Type your username, it will auto-fill the URI in the next textbox
- Go to the URI textbox, change the URI
- Click on Log In
Result: the URI will revert itself to the version of
http://username.wordpress.com just prior to clicking Log In. It's possible for WordPress to have a different username than the subdomain name (as in my case). And if you allow people to change the URI anyway, why reverting it?
I tried this in Firefox, not yet tested in other browsers. Workaround: type the subdomain name instead of your login name in the login name field.