Yes they have re silent voices.
For me, I was working in financial services in London. Without my super supportive boss, I would never have been able to go on the Trial. The 'climate' I was working in, I would not have been able to continue my career had employers had any inkling of the health issue. Because with what I was doing - projects and troubleshooting with highly sensitive data and deadlines ie very high pressure work at a managerial level, it really mattered that there was no hint of 'unreliability'. I'd been contracting for half a decade, and I dont' think I even told the Agencies I used until after the Trial was over, and I'd become friends with some of the agents working with them repeatedly that I told them. Oh I also told a doctor at a work medical for the last contract I did late 2011, he said to try it and if I got exhausted, walk away which was sensible advice I feel! I think he said he didn't see a need to report it to the prospective employer as it wasn't well recognised (I'd have got a 'fail' and lost the contract if was I think).
I think it was only when I became severely affected a few years ago, that I realised that I'd probably never work again, so there was nothing stopping me coming out of the 'me/cfs closet'. Obviously people noticed my energy levels did random things but it was never discussed what it was, unless it was close friends or family. Also, I don't think I actually was genuinely unwell with something I couldn't get fixed until I went severe. Before that I always had a sneaking suspicion I was just being a bit feeble. I remember one time a close family member asking if maybe it was in my mind and I enjoyed the attention I got for being ill (sigh, that was long after the Trial but I was still moderate. And to be fair to him, he wasn't well himself. he didn't mean it unkindly. but still). It is hard for the people around you to understand that it's real, cos it fluctuates, and it's hard for us as ill people to understand it too.
Also, until I became severely unwell, I spent very little time on things like FB and hadn't even heard of Phoenix Rising. I wasn't even part of a physical actual ME/CFS group (though I knew they existed - partly cos the Trial people asked me not to join one til after the Trial, and after the Trial I wasn't up to trying to find parking to go to teh meetings). I was all wrapped up in my little world of trying to keep working and not doing much else.
I think people who were well enough to be on the Trial are probably in that position, desperately trying to hold it all together, trying to keep working, look after a family or whatever - it wasn't til I realised via David that there were wider issues to teh trial than I'd thought. Others maybe just aren't aware of the issues. Or have a need to keep their involvement private due to concerns about employer attitudes or family & friends attitudes. I don't know though, I can only speak for myself.