"Graham is guarding against what can go wrong. Fisher is looking at what can go right." Gary Mishuris sees both personality and experience shaping an investor's approach. Copying the style misses a more useful lesson: "The thing you should copy is that you should be your own person."

This week's oil rally has revived inflation worries. Retirees face a double hit when rising living costs force bigger withdrawals from a falling portfolio. In an earlier conversation, Bill Bengen described that combination in his historical worst-case retirement sequence: "Multiple big bear markets, followed by high inflation, which forced 'em to increase their withdrawal, just devastated their portfolio."

"If you improve the backtest, you're improving the backtest. That's all." Rob Arnott on confusing a better historical fit with a better investment strategy: "Scientific method is have a hypothesis and use data to test it. Don't use data to find something that worked ... and use that to create a hypothesis for why it worked."

You can reduce portfolio risk without making an all-in or all-out market call. Paisley Nardini: "Most of us ideally are living somewhere in the middle of this." That can mean de-risking or diversifying when headwinds build, while still participating in the upside. Volatility "is a feature, not a bug of being invested in the equity market."

A business moat is not a substitute for trusting the people running it. Michael Baron will sell if a management transition puts someone in charge he does not believe in. But a new CEO is a reason to reassess, not an automatic exit: "We reassess who that person is, what are their motivations, what are they trying to achieve, and whether or not we believe they'll be successful."

"The portfolio you can actually stick with will always outperform the one that you're gonna abandon at the wrong time." "When you add other things that are a little bit outside of your domain of expertise, start small, build intuition, operate from a position of strength." Mike Philbrick on the one lesson he would teach the average investor.

More than half of Andy Constan's work goes into figuring out how his investment thesis could be wrong. "The number one thing I wanna do is just evaluate where I could be wrong." Considering the opposite case can change his mind, strengthen his view or change how much confidence he puts in it. "I can't imagine a scenario where I could blindly assume I'm right and expect to survive."

Producer prices rose 6.3% over the year to September. Should your bond allocation be judged only against inflation? In an earlier conversation, Cullen Roche described nominal bonds as "principal stabilizers": "They should be owned to create principal stability across very specific time horizons." For him, that means "probably high quality and shorter duration" to create "a pretty high level of predictability."

A quarterly earnings number matters only if it changes what the business is worth over the long run. "What it makes in a particular three months is not life-changing." Colin McQueen holds stocks for a little over four years on average. He looks for "material information" about future earnings, then asks: "What is it worth, not how it's gonna react to the news flow."

Cutting risk after losses can quietly weaken a good trading strategy. "For a long time, if I lost money five days in a row, I'd be, 'I better take it easy today, go to 30%.'" Brent Donnelly realized he was reducing risk after drawdowns and increasing it after unusually good runs. "If you have a good process ... and you know the difference between variance and actual bad trading where you're not following your process, then you can maintain a way steeper slope of your P&L."

Tech spending doesn't have to collapse for tech stocks to lose leadership. Jim Paulsen compares technology-related spending with its long-run trend. His concern is the speed of the recent expansion: "It's just too extreme, too much, too fast." "Even if it stays fairly strong, if it just is less strong, I think that's gonna have an impact on leadership."

"I think it largely gets the direction right, but the magnitude wrong." Expensive companies can grow faster and still fail to justify their prices. With earnings expectations helping push stocks to record highs, Cliff Asness's research asks the relevant question: did growth over the next three or five years match what investors paid for?

A passive portfolio can hide an active bet. "You're really actively choosing to bet the farm on one thing." Jason Hsu worries that investors buying the S&P 500 for diversification may underestimate their exposure to the same AI growth story.

If SpaceX joins the S&P 500, index funds could rush to buy from holders who do not want to sell. "Like a herd of elephants trying to get through a revolving door at the same time." Rob Arnott argues that funds trying to match the index's closing price can crowd into the same trade. Minimizing tracking error does not necessarily mean getting a good purchase price.

"All too often, people assume that something as complex as financial markets requires a complex solution, and it really doesn't." "The key to success is just minimizing mistakes and not interrupting compounding." Peter Lazaroff on the one lesson he would teach the average investor.

Last week's AI selloff puts an old investing problem back in focus: a technology can change the world without rewarding the people funding it. Ben Inker's earlier warning: "You get way too much investment and you destroy that ROI." "It doesn't mean that the technology doesn't change the world."

Tom Maher on when basket trades overpower company fundamentals. "People hate company B, and this is in a basket with company B, so it's getting dragged down." These moves can persist for "six, nine, 12 months, not one or two days."

Better or worse may matter more than good or bad. Jim Paulsen on why changes in expectations matter more to asset prices than whether the economy looks strong in isolation.

"The surefire winners of the internet boom were Yahoo, AOL, and Cisco." Chris Davis sees a warning in treating today's AI leaders as inevitable winners.