This is just a general response after reading all posts in this thread:
My forum is going on two years old. For the first year and a half, I had literally no content and no users to create content. I was busy. However, since I do have an SEO background, I did optimize the forum in all the right places so that when people were searching for "debate forums", and other keywords/phrases, my website would be the first on Google and other search engines. It is possible to optimize a forum without content. Having content, however, is better for optimization purposes if you want to target people searching for specific topics and areas of interest. Also, every website, even professionally, that I optimize reaches page one of all major search engines without link building, no matter how old the domain is. Ugh, page rank is a myth that I wish would just fade into the night!
Once you know how to organically SEO websites, and have tested your methods numerous times (and have maintained your SERP results for a year and longer), it is surprising to hear others say how difficult it is to SEO a website. Organic SEO is not a myth, but because so many people obsess over what they can do to boost their sites to the top, myths are created involving too much junk that just simply isn't needed.
When I first started out, I had to remind myself, from my own SEO testing, that moderation is key. Keep it simple, clear, and to the point. I see so many websites whose owners clearly tried too hard to SEO them, and all they've done is create jumbled madness without a method -- and they inflict attention deficit disorder on their pages.
Have you ever tried to follow the conversation of a person afflicted with ADD? If their brains are going through rapid cycling, which junk websites appear as to the SE spiders, it's difficult to make heads or tails out of what's really meant to be said, seen and heard.