So, I thought about a lot and finally found that Your format is fitting very well, but that it would need some more years to have a real standard.
Now, thinking about one authors question how to make sites more public i thought about a special "friendly sites search" based on this format.
For example: One has a site mainly featuring travel, another one a site about flights and a third one a site about insurances.
If someone now searches on the travel site about questions regarding flight insurance, may be he does not find something. On the insurances site he would have more luck and on the flights site as well but he does not know about.
The solution I was imagining would be some kind of "extended" search, where the travel sites owner could offer a search on some friendly sites as well, for example the mentioned insurance or flight sites.
After a normal search on the travel sites without matching results, a button could show up, like:
Do You want an extended search on related sites ?
Choose of the following...
If the visitor accepts, automatically the flights and the insurance sites are searched as well. Due to the microformat it should be unimportant how each sites owner organized his sites (comments, answers ...).
There are many advantages in this I believe at least.
A searching vistor stays inside Your web, friendly sites are linked and get PR as well as visitors and finally the microformat could become kind of a small standard.
I hope this is not too far away from Your plans, but i really think it would work very well for all participants with specialized sites or interests.
More kinds of usage are thinkable as well like friendly sites realted to tags and more...