With 1PW 7 beta for Mac, the username field on https://www.gpforums.co.nz no longer fills, the password field does though. This worked fine on 1PW 6.
Also, 1PW doesn't offer to save credentials (I tried deleting my existing login to try see if the username field had changed)
The login box is hovers over the login link:
1Password Version: 1Password 7 Version 7.0 (70000019)
Extension Version: 188.8.131.52
OS Version: Mac OS
Sync Type: Not Provided