It is possible to write reasonably maintainable code that is also lean and efficient. It just takes a little care and knowledge. The problem is that a lot of this knowledge is what most people (even me) would call premature optimisation when looked at in isolation.

All nice points! But wrt this last point I feel like differing: the vast majority of all instances of premature optimization I find worth pointing out, and "condemning", as such are for speed, not certainly for maintainability...