Sam I kind of wish Navindra had picked another name for this from than "Adult Beginners". At least over at the other forum which shall not be named, the "Adult Beginners Forum" name was a source of confusion and a definite misnomer. Most of the people hanging out there were no longer beginners. I suspect that will be the case here as well.
When I first started contributing to the ABF I might have been a beginner, but now, 15-16 years later - I am not.
"Beginner" is such a difficult term. I still feel like a beginner. A year ago, I was working through Bach inventions trying to play them well, and really struggling with left hand dexterity. I'm still working on developing some aspects of basic musicality. I am still nowhere near professionals in terms of how I play. In those ways, I feel like a beginner.
But I am considerably more advanced, and can sometimes hold my own in front of university students. So it all depends. If you look at the level of playing, I might be able to pass a grade 8 or even diploma exam in a few months. But I'm still pretty green, and have only been at it for a relatively short while.
A forum like "Pianist Corner" will tend to attract professional pianists, piano professors and the like, active accompanists, performers who go to national/international competitions. Compared to them, I would fit in much better at the ABF.