Your first comma separates two independent clauses. Thus, it is correct. The second comma has nothing to do with that.
Here is a sample sentence with the clause arrangment in question:
She is certain about it, and if she has a backache, she will take medication.
I believe this sentence to be punctuated correctly.
I need the brilliant and helpful people here to tell me how to explain to someone why a "comma plus and" can legitimately separate an independent from a dependent clause.
I think of "if she has a backache, she will take medication" as something like a unit, which is why it can take a "comma plus and" to separate main from dependent clause--because the main clause is following right behind the dependent clause.
Does my "unit" concept pass muster with the educators here?
Last edited by emsr2d2; 15-Jun-2015 at 00:19. Reason: Enlarged font to make it readable
First of all, my question is about the first comma, not the second comma.
Second of all, "if she has a backache" is a dependent clause, not an independent clause.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
Another justification for the correct placing of the comma, is that if two commas are used parenthetically, as they are here, the phrase within them should be able to be deleted and still leave a grammatically correct sentence.
With "She is certain about it, and if she has a backache, she will take medication.", this doesn't happen.
"Comma style has changed over time, and probably will continue to."
"Comma style has changed over time and, at least as I see it, probably will continue to." OR
"Comma style has changed over time, and, at least as I see it, probably will continue to." This is probably most correct, but, as with full stops, the number of commas used is possibly decreasing.