As I understood in example with D language you use dictionary which is realized with hash table. But in C++ example you use map which is realized with balanced trees. But hash table is faster than balanced trees.
In the section "Filling a String", shouldn't the D example use [2..3] instead of [1..3] ?
No, arrays are indexed from 0 so the second element is at 1. The slice is open on the end so [2..3] would just be str = '?'.
A typo "All copy-on-write is is" -> "All copy-on-write [means] is".
In "Interoperability With C String Syntax", the second code sample is D and should be highlighted for D syntax.
These could be submitted as a bug: http://d.puremagic.com/issues/
Corresponding page in the D Specification