Exactly my point. Now, the interesting question is whether you have a smaller total number of bugs, and amount of impact, with this architecture or that architecture. I don't know about that, but if you are measuring the reliability of microkernels "exactly the same way as any other complex piece of technology", you must keep in mind that you are probably measuring the behaviour of a smaller and simpler thing, and the risk for bugs has been offloaded somewhere else, it has not disappeared.
You have a much smaller number of bugs because (a) each component is much simpler (b) runs as a separate process and so can be debugged and worked on by mere mortals and (c) works using a well defined interface (message passing) which makes testing and debugging a much simpler affair.
