VCs can probably tell a 5 apart from a 3, but it doesn't matter because neither a 3 nor a 5 is someone you want to fund. They can't tell a 7 from a 9, is what I'm saying. If they're not dealing with people of similar pedigree and experience, they may not be able to tell a 9 from a 5, even.
I think that "ranking people" is a fascinating topic in itself - unlike some, I do think there is validity to doing this although you have to be really careful to avoid bias, and to measure against the proper scale. I'd be interested to understand yours!
[1] They aren't always: https://en.wikipedia.org/wiki/Lev_Landau#Landau.27s_List
He has written a ton of stuff about VCs, programmers, etc. His riffs on the Gervais Principle are really good. He followed that up with some other gold.
The scale-of-10 stuff is his concept of how there is a mismatch of skill and power in the tech business world -- particularly between the programmer and the business folks. For example, highly-rated business people don't even work in tech -- they do other finance like private equity or hedge funds. That means that most of the top VCs are maybe 7s, and they're bitter about their relatively low status among their B-school peers. That also means that the top tech people (the 10s) struggle to find business people who are their equivalent of awesomeness. This is a short summary.. read the original stuff on the blog.
Some folks on HN do not like MO, so they seem to downvote him out of principle rather than based on the content. While I think that his tone can be terse at times (it seems to have gotten better in the past year or so), the content is often frighteningly spot on. I think that this makes some people uncomfortable.