When you are doing a research paper or a writing and you have two people doing it, do you put a comma before the and in something like... By Arielle, and Bella?
If you cite a source following a style guide like the APA Manual, you may encounter something like the following:
Mohnkern, K., & Maiuro, A. (2016). A heading on a paper. ...
Here, the comma before the "&" is the closing comma after the parenthesized abbreviated first name ("K.").
Maybe you saw something like this and thought it applied to all lists of names?