He isn't arguing there is an actual flaw, he is arguing that the feature isn't identical to what he hypothetically wants He doesn't give practical problems with it, just hypothetical problems.
For example, he says it's hard to tell 'the importance' of a fork. The importance of a fork is whether or not it is the original project, or a fork. If it's the original project, it's what you were looking for. If not, it's not, unless you were looking for a modification or feature missing in the original. In the latter case, you don't need to see the 'importance', whatever that means, you need to see the diff. Or have someone recommending it.
Anyway, the post just rambles for pages.
Speaking of flaws, HN has one big flaw, which is not showing sub-domains (and thus tricking me into clicking this link, thinking it was an official github thing).