Including fees, commissions, and intraday trading revenue in P&L calculations could distort the true relationship between actual losses and the VaR estimate. These items are unrelated to portfolio risk but can offset trading losses, resulting in fewer observed exceptions during backtesting. This practice would make the VaR model seem more accurate than it truly was by underrepresenting the frequency and magnitude of exceptions.

B is incorrect. The issue was not about underestimating VaR but about distorting P&L figures used in backtesting. The inclusion of non-risk-related items in P&L artificially reduced the observed exceptions, creating a false impression of the model's performance rather than directly influencing VaR estimates.

C is incorrect. While different reporting standards can make comparisons challenging, it doesn't make them impossible. The primary problem was the distortion of individual bank’s backtests.

D is incorrect. Including these items in P&L calculation does not add significant computational complexity to VaR calculations.