Doesn't mention QNX or Redox in it's comparison page (that is really nice and self reflected by the way), would be interesting to chat about where in the design space it wants to differ, because QNX takes great pride in having optimized synchronous message passing.
Neither the whole L4 line of work, which fundamentally rely on synchronous, rendezvous-style IPC as their primary kernel-level communication primitive; the transition to synchronous IPC together with the specific way it was designed was absolutely central to the dramatic performance improvements of L4 over first-generation microkernels like Mach. QNX independently pioneered many of the concepts that define successful microkernels.
