The Tau Manifesto author here. Don't yell it too loudly, but I strongly agree: e is by far the most important of these numbers. But e is the natural choice, so I don't have any bone to pick with it. (Bob Palais made an analogy in "Pi Is Wrong!" Suppose e were defined as 1/2.718281828... Then there would be confusing negative signs everywhere. Exponential decay would have a positive exponent, etc. Such is the case with τ and π, with a factor of 2 in place of a factor of -1.)