The two opinions aren't mutually exclusive. I simply read you to say that co-founders are a trait of successful "startups". While here the opinion is that's a fine trait, but it isn't always necessary. To me, it's just an disagreement about necessary and sufficient conditions.

Paul, would you agree that a co-founder makes many things easier, but the right single founder can find that support structure through other means (e.g., spouse and a few core employees with significant stock)?