Note: I'm posting this comment to Chan's post as a new entry because I'm apparently not an Edit Hawaii Team Member, only a Contributor. It hadn't stopped me from posting comments before, but now it says "Comments on this blog are restricted to team members." So I'm emailing Pat for an invite now... O:)
I *think* the sentence is fine with the commas*, but I'm not the resident expert here or anything, that's for sure. haha
I think your AP teacher was right in telling you that rule when it comes to "commas that enclose," according to my Scott, Foresman Handbook for Writers, 6th edition (That comma is there because it's written by two people, apparently. haha). Here are some examples:
Commas that mark nonessential (nonrestrictive) modifiers
Neil Armstrong, who was born in a small Ohio town, was the first human to walk on the moon.
Commas that enclose nonessential (nonrestrictive) appositives
George Washington, the first President of the United States, served two full terms.
But I think the sentence in the article is primarily using a comma to "link" (again, I'm referencing the SFHW) the two independent clauses.
[Jason] faced a lot of criticism, but ...[he] used it to his advantage.
I eliminated the "instead of dwelling in the negative" in the second part of that sentence because I think it uses a comma for a different purpose there.
The book calls the second usage "commas after introductory subordinate clauses," which can be signaled by words like although, if, when, because, as, after, before, since, unless, and while. I think you can also call that a dependent clause.
I like to think of it as needing a comma because the order of the parts in the sentence is reversed.
Jason used [criticism] to his advantage instead of dwelling in the negative.
Instead of dwelling in the negative, Jason used [criticism] to his advantage.
So I think the sentence in the article is using each of those commas in different ways — first linking, then introducing — so it ends up looking like "commas that enclose," where you would take out the portion of the sentence bracketed by the commas to see if it stands alone as a complete sentence.
But again, big asterisk here!
* I didn't take Modern English Grammar from someone who wanted to teach grammar, so I don't really know all the rules. :-\