I think you misunderstood me. evo_ is saying that it's unfashionable to talk about it when you use Microsoft software. I replied that in my experience the reason startups don't talk about Microsoft stuff is that they're not using it, not that they are and are embarrassed to say so.
It may well be that YC-funded startups consistently differ from the average startup. But that doesn't mean that such differences are due to fashion. The kind of people we fund are more consistent in knowing what they're doing than in being young. So if as a group they differ from the norm on technical matters, the more likely hypothesis is that the norm is lagging.
I would think that the majority of startups aren't using MS products, but I understand that the ones that are might prefer not to talk about it for fear of ridicule by the hacker community.
I'm comfortable assuming that the YC startups are above the average, but that doesn't mean they aren't also affected by the demographic that would most benefit and be able to participate in the YC program. In no way am I implying that YC would select someone younger for admission over someone more qualified - just that the nature of the program self-selects.
In my case, I'm still young but having a toddler puts me in a similar situation to a typical older entrepreneur. It would be incredibly difficult for me to take an X month block away from my family or to uproot my family. And a $10K investment doesn't mean to me what it does to a college grad, because I can make that in a couple of bonuses or consulting gigs. The thing I miss most in a program like YC is the mentorship, but for me it's not worth the aforementioned hardship.
It's not that I'm not interested in new technologies, I do tinker, but it's just a matter of priorities. Given that, you're probably right that the "norm" would be lagging in terms of using the newest and coolest technology. I don't think that equates to generally worse companies, just less fashionable, to tie back to the original point.
It may well be that YC-funded startups consistently differ from the average startup. But that doesn't mean that such differences are due to fashion. The kind of people we fund are more consistent in knowing what they're doing than in being young. So if as a group they differ from the norm on technical matters, the more likely hypothesis is that the norm is lagging.