Technical manuals frequently contain grammatical errors like the stray comma you found there.
Your question B is the only correct one. Subjects and verbs are inverted in questions, so question words like why, how, when, etc. must be followed by a verb when they introduce a question.
Affirmative: A comma was added.
Interrogative: Why was a comma added? Where did they add a comma? When do I need a comma? Why do I use a comma? How do I know I need a comma?