Dear Jochen,
I followed your link concerning relational quantum mechanics. I appreciate the author's attempt to clarify the foundations of quantum mechanics, but I do not agree, especially out of my specific understanding of Special Relativity, which Rovelli considers obviously as uncontroversial.
I am convinced that Special Relativity (SR) is incomplete. This incompleteness concerns the speed of light. My view is: As the quantum mechanical concept of Wave-Particle duality has shown us that light is of dual nature, I came to the conviction that the speed of light c has to be of dual nature, too. In other words: The speed of light c is given twice, in a wave-like version and in a particle-like version. In SR only the wave-like version of c has been taken into account.
As the result of this incompleteness the relativistic Lorentz symmetry is too restrictive. I've found a geometrical space-time-structure that fits to this "Dual Parametrization of c". According to this structure there are two space-time-branches, which I am calling the "Gödel-Zone" and the "Gödel-Trench". The Gödel-Zone (from v = 0 to v = c) is limited by the speed of light v = c, whereas the Gödel-Trench (from v = c to v = oo) is limited by the speed v = oo. In SR the second space-time-segment (here described as the Gödel-Trench) is completely missing.
If this second segment is really existing then we have to strive for a deeper understanding of SR - and not of quantum mechanics. That is at least my position. But I admit all these thoughts are more a vision than a coherent theory.