Consider specifying what whitespace means in the format specification

The format specification document indicates that “any amount of whitespace may be inserted between terminals”. Please consider specifying which whitespace characters are allowed exactly (or permitted / tolerated / works but is highly discouraged…).

From the examples section I understand that new line characters seem permitted, for example, not just U+0020 SPACE.

As a more specific question: is there a recommended encoding for newlines (Windows / Mac / Linux)? Are all three spec compliant?