I have a couple of suggestions that I think would improve the forum:
1) Divide the forum into sections:
For instance, there could be a section for user complaints, a section for general questions about Chinese characters, one for grammar, perhaps even a section about Chinese culture/history. There could also be one for recommendations, where users could recommend books, textbooks, movies, etc to each other. These are just off the top of my head, but I'm sure other useful sections could be introduced too. How about a section where users are only allowed to post in Chinese? Advanced users would benefit from that, and it would be a great advert for the site.
2) Arrange by most recent posts:
In other words, when a reply is posted on a thread, that thread would be instantly bumped to the top of forum. That assures that useful threads don't get buried under a pile as new threads pop up, being inevitably forgotten. Also, it keeps people discussing things that are relevant, whereas the threads that become irrelevant get naturally pushed to the back.
I think this is particularly useful when, for example, a thread is started with a very specific question in mind (e.g. what's the pronunciation of "X" character, or "what does this sentence mean", etc).
Also, having a section for "General questions about Mandarin" or something like that would condense all of these threads into one, making sure that people can have direct access to more threads which they might find helpful, but wouldn't necessarily have looked for without seeing it first.
For instance, I was working my way back through the pages of the forum and found a thread on Chengyu that I found very useful. But without doing that, it simply would've got buried in the back, and in a couple of years time, no one would even know of that thread.
I really think the site would improve a lot from user-generated content/discussion, and I believe these adjustments would both facilitate and encourage users to become more engaged in discussions that would help each other. At the moment, the content generated in the site is mostly produced by the staff and consumed individually by members. On the other hand, I think the site should encourage members to generate content by themselves and for each other.