The problem is (imo) that he's writing for himself and not an audience. It reads like a stream-of-consciousness journal entry, not a thoughtful attempt at relaying information to another mind. A good start would be learning to self-edit; the length could be cut significantly with no real loss of content.
What's particularly aggravating is that he knows, more or less, what clear, concise writing is (cf. his discussion of "classic style") and goes out of his way to not write like that. Yes, I read his justification. No, it's not good.
Someone is going to chime in by saying that I must be wrong because his articles frequently reach the HN frontpage. But correlation is not causation. The actual information content is generally really good – that's why they're popular. But they'd be even better with more attention to the mechanics of writing.