Awhile ago when we changed from the older-style "First and last name" at registration to "Single-word username" system as part of display names improvements, single-username Residents could view, but couldn't post to the forums and blogs here at blogs.secondlife.com.
After much tussling, we've fixed it as shown here, so go ahead and make your voice heard! I know it was terribly frustrating from the many messages I got. Our apologies it took so long, seeing as how important it is that you can ask for help from your fellow Residents in Second Life Answers... and I'm guessing you have a lot to say. Single-username logins also work at the Bug Tracker.
Related, single-username logins to the Second Life Wiki still don't work, meaning newer Residents can view, but can't edit the wiki help pages. We're still working on this and if it seems like we've gone strangely silent on giving updates, just ping me and I'll check with our tech experts to see what's going on. I promise.