- This recipe, makes 24 servings as an appetizer.
- The author's background, qualifies her to write with authority about this subject.
Huh? There's no need for a comma in either of these sentences. If there were some explanatory details between the subject and verb, a comma might be necessary. For example:
- This recipe, which came from my aunt's cookbook, makes 24 servings.
- The author's background, which includes 15 years as a gynecologist, qualifies her to write with authority.
I think writers do this because they aren't sure what the rules for commas are. They scatter them like snow throughout a piece of writing; the result is often a mess that's hard to read and harder still to understand.
The rule is subject-verb, not subject-comma-verb.