Yes I saw the thread. If the rules were being written today, everyone would have 'ADSB' and for most en-route airspace pilots would self separate with ATC coordinating traffic in busy areas.
The core fact for FAA trained pilots to understand is the FAA infrastructure doesn't exist here - you either live with it or don't fly in IMC OCAS (as you can't count on a Radar Deconfliction Service).
In the US an operation of this sort would have your ticket pulled due to reckless endangerment (i.e. the regulatory belief you will hit someone or something if you fly blind with no separation/coordination). The CAA clearly have had a view for years this is a reasonably safe activity (and for what ever reason, the accident rate (of 0) doesn't refute this view). I do recognise this may simply be due to very few people operating IMC OCAS with no service (like the Concord - a very small fleet so 0 fatals until the day there was one, at which point it moved from the safest (0 fatal accidents/1000 flights) to the worst safety stats of any modern airliner).