The external fund manager backed by Berkshire Hathaway’s Charlie Munger, Li Lu, makes no bones about it when he says ‘The biggest investment risk is not the volatility of prices, but whether you will suffer a permanent loss of capital.’ When we think about how risky a company is, we always like to look at its use of debt, since debt overload can lead to ruin. We can see that Liberty TripAdvisor Holdings, Inc. (NASDAQ:LTRP.A) does use debt in its business. But should shareholders be…