I'm joking about Linux, of course. Nevertheless, this question really interests me. I understand that systems they work on in Microsoft are large and complex. I know very well that bugs may be detected by users only some time later after release. But I don't understand how can one simply not notice obvious bugs in the tools the developers themselves are meant to use regularly?
A few words about classic mistakes to start with. Everything's clear about them: developers may well miss them because they are not the end users. A good example of this is an error in one of the Microsoft Visio versions. It was the 2010 version, I suppose. When you started typing text in Russian into a Basic Flowchart block, it was being typed back to front. I can understand it. Someone has mixed up things and decided that words are written from right to left in the Russian language. Russian and Arabic are absolutely the same, or very similar at least. There were no Russians among testers, and the error got into the release version. I can understand this case.