Visuals are the big missing piece. Any text-based discussion will build different visions in each reader's head. Often, everyone agrees on the text description, and then, when a designer draws a picture, everyone disagrees because they weren't really aligned, they all assumed everyone shared their own personal vision. I love the concept of building a better way of discussing things asynchronously, but I would put visuals (images, videos, diagrams) at the center of that forum and overcome the biggest issue with visuals -- that they are often hard to make for many people.

All the mentioned alternatives tie comments to a particular user and relate comments (responses) to other comments. Instead, the conversation could be focused on the topic of discussion, which is often best described as a set of visuals describing the concept. Rather than responding to comments, you could organize comments around the associated component of the problem as it is described visually. This would allow multiple individuals to support a concept, rather than just amplifying or criticizing a particular user's comment. This might even help avoid defensive behavior since the problem is the focus rather than a particular person's comment.