> What Xanadu has that others don't:
> When responding to any argument (for or against something), you will be able to comment on each and every relevant sentence. The document you are commenting on will automatically link to your analysis. Whether readers of the document see your comments or not is up to them. They will have filtering tools to include or exclude whoever they want. That is their decision to make. Thus every possible viewpoint can be heard and can cross-comment on each other as much as desired.
This could be an extension of Twitters behavior, to link your analysis directly into other peoples document.. And we all know what great social collaboration happens on Twitter ..