I think this is more important than just diversity in tech (and that is important) - and I'm a relatively recent convert to caring.
We all, even founders, benefit from diversity of founders. If start-ups predominantly get started by similar types of people you're missing out on competition and innovative ideas. I think this applies not only to general business concepts but especially to domain areas.
One of the things that infrequently crops up on here is how much money there is to be made in Spanish language Christian apps, as a WASP I'm less likely to have the domain knowledge to break into that market. So it does seem rather odd that VCs might be missing out on being able to profit from a market of ~23m.
Then there are more social good focused start-ups that might emerge. Given all the problems the US has with racism and sexism I'd posit that a black female founder might be a good bet if they had an idea to try and improve things.
I was interviewing a white university student the other day who had managed to get through 2.5 years of a Computing degree before realising she was capable of being just a good developer as a man. Not that she was as good, just that she actually could be a developer, rather than being assumed to be the management / documentation type. I'm nowhere near Jon Skeet on the feminist scale but it really made me think about how under represented groups can be put off.
And that is the point of the article. The top thread on here can be arguing about whether 0.1% is "statistically zero" because what matters is perception. If a potential black female founder perceives an industry as being unwelcoming they're less likely to enter it. There is a massive opportunity cost to get to the point where you look for VC funding, it isn't an experiment you can just run on a whim. It is quite possible that the calibre of black women who could be founders are looking at the startup world and heading in another direction where there are much stronger social signals that they are likely to be accepted.