Uknmy, I think that would be way too hard and akward to do, lots of people dont even know their subgroup when they come here and how would one distinguish the subgroups. There seems to be quite a few different ones beyond just the CFS or ME thing eg the EDS/POTS/mast cell disorder combo subgroup seems to be a possible distinct group.
The best thing to do if to get to know the regulars and work out who has like illness so to know who posts may contain the most useful advice for you. And when it comes to studies.. check to see how the participants were picked to see if it fits with your own illness. eg I think Im at much greater risk of getting thyriod cancer as I matched the selected participants in one ME/CFS study who also had certain other issues and the study showed a much higher risk of this cancer with that group. It was recommended that those who had all those things have a scan every couple of years for thyriod cancer due to the increased risk.