I think that having one foot in both camps is probably a reasonable way of continuing to exist rather than treating yourself as fully recovered and that ME/CFS is no longer relevant in your life.
Yes, it seems to me that our disease, more than most other diseases, allows many of us to experience periods of relative health in which we may not signal any particular "illness behavior" (assuming we've been practicing "illness management"). For example, I am able to go to work a couple of hours most mornings, socializing fairly normally with my co-workers who have no real comprehension that I will, afterwards, have to spend much of the remaining day recovering.
I can understand why this type of research doesn't appeal to a lot of us. As a grad-school grad, I'm accustomed to jargon, and I find it kind of interesting on a meta level (ha). Habermas believes "the self" is a collaborative creation by an individual and the society she interacts with. I.e., society is our mirror. Since society "gets," say, cancer, or diabetes, people with those diseases likely receive clearer reflections (in the form of empathy, discussion, insights, etc). So, those "selves" might feel more solid and well-formed (less liminal).
But, on top of that, we experience additional blurriness in our own community, not only because our relationship is largely online, but because many of us with very similar symptoms and challenges might actually have had very different etiologies, triggers and responses to treatments. So that can multiply the fun-house effect.
Anyway, Dolphin, I thought you shared some great insights. The ability to work/study full-time seems a useful demarcation, not only for perceiving our own lives, but for "civilians" who think they understand what we're going through because they get pooped out easily too!