This is a silly argument and a misinterpretation of the purpose of orthogonality. Orthogonality is not a goal in itself, nor is it's purpose to eliminate redundancy. It's a tool to reduce entanglement of features. It helps simplify designs by ensuring that changes to one feature do not affect other features. This reduces the chance of unintended or inconvenient side effects when making changes. This is helpful for software architecture in general, not just programming language design.
This is from 2006 and there's been a lot of water under the bridge since then. Ian is an exceptionally smart guy and one hell of a hacker, I wouldn't care to hazard a guess as to what he thinks now. Perhaps he'll drop in and enlighten us.