Good piece. My suggestions:

1)

But real people regularly ruin their lives through sloppy investing, and for them perhaps it is better just to say that beating the market can’t be done, so just buy, hold, and forget about it. We, on the other hand, believe a more nuanced understanding of the facts can be helpful.

Beware overconfidence. Even sophisticated investors such as college endowments often fail to beat simple index portfolios. http://johncbogle.com/wordpress/wp-content/uploads/2011/09/NMS-9-12-12.pdf

It is extremely difficult to find a strategy that outperforms the market, net of fees, and then stick to that strategy for years and years.

2) Even if you’ve discovered a way to beat the current market, the market adapts. See paper, “Does Academic Research Destroy Stock Return Predictability?” http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2156623

3) You seem to view portfolio risk as merely a potential cause of behavioral mistakes, but risk can also tangibly affect an investor’s long-term goals. During the withdrawal phase, the likelihood of portfolio exhaustion can be increased by negative performance, especially at the beginning of the investment horizon.

4) You forgot about the low-volatility anomaly. Extending this idea across asset classes suggests a lower allocation to stocks and a greater use of leverage. https://www.aqr.com/library/journal-articles/the-low-volatility-anomaly-market-evidence-on-systemic-risk-vs-mispricing