Rule for comma in front of and

[Debra Kirk]

She appears frail, and sad, but in no acute distress.

Is this grammatically correct and what is the correct rule for using commas before the word "and"?​

 

[MikeNewYork]

She appears frail, and sad, but in no acute distress.

Is this grammatically correct and what is the correct rule for using commas before the word "and"?​

The comma between "frail" and "and sad" is unnecessary. The comma after "sad" is OK, though many would omit it.