Consider the following example:
To add to the confusion, every New Year’s Day a person, according to this Korean counting system, becomes a year older, regardless of his or her actual birthday.
This clause is restrictive as “his or her” refers to “person”. So, then why is there a comma?
Answer
You can remove “, according to this Korean counting system, “ without changing the meaning of the sentence. A non-essential element like this is always surrounded in commas.
“His or her” doesn’t have anything to do with the placement of that comma.
See below:
To add to the confusion, every New Year’s Day a person becomes a year older, regardless of his or her actual birthday.
https://owl.english.purdue.edu/owl/resource/607/05/
Attribution
Source : Link , Question Author : G.B , Answer Author : Mako212