See that comma after the closed parenthesis in the title up there?
That’s where it belongs. This isn’t a style issue. It’s a mechanics rule in AmE. (I suspect it’s the same for BrE, but I couldn’t find an entry for it in my copy of the New Oxford Style Manual.)
I’ve lost count of how many times I’ve seen someone write a sentence with a parenthetical intrusion and put the comma before the opening parenthesis, like this:
I was walking with my mom the other day, (doctor’s orders, you know, after her surgery) and we saw blah blah blah.
It looks so odd, I stop dead every time. Think about it like this. You’re talking along to a friend, okay? And you interrupt yourself mid-thought to add something, but that thing you’re adding actually belongs to what you just said, not to what you’re about to say. It’s semantically and syntactically linked to what came before. In my example, the comment about doctor’s orders is linked to walking with Mom, not to whatever thing we saw.
That’s why the comma goes after the closing parenthesis of the intrusion. We keep the related thoughts — the main one and the related intrusion — together by putting the comma afterward. Of course, this is assuming you need a comma. I’m not going into the variations that don’t. This post is short (remember the title?), pithy, and about commas.
See? I just did it again in the last sentence of the previous paragraph. That’s how it’s done.