The use of comma between adjectives

Solution 1:

Whether a comma is required depends on the intended meaning.

Inserting the comma in "bold, fresh voice" would give 'coordinated' modification, so "voice" is modified by a coordination of adjectives, giving the meaning "voice that is both bold and fresh".

By contrast, omitting the comma in "bold fresh voice" would give 'stacked' modification where there are two layers of modification: "voice" is modified by "fresh" to form the nominal "fresh voice" and this in turn is modified by "bold", allowing a somewhat different interpretation - "voice that is bold by the standards applicable to fresh ones".

In the example you gave, the author presumably omitted the comma intentionally, so we interpret it as stacked modification. He could of course have simply got it wrong and really intended it to be coordination, but omitted the comma in error. Who knows?