Better sentence-writing in 30 minutes a day - Dianna Campbell 1995

Mid phrases
Using commas to set off phrases
Punctuating sentence combinations

We’ve been working with phrases that come before or after an independent clause, but a phrase can also appear in the middle of a clause. When it does, again you have to use your judgment to decide if it should be set off with commas. If you think that a pause and a shift in vocal pitch are required, then use two commas—one before and one after the phrase. Read these sentences aloud and notice how helpful the sets of commas are.

(a) The new shopping district, in spite of careful planning by the town council, did not turn out to be much of a success.

(b) Your cousin, with or without his Doberman pinscher, is not welcome here today.

(c) The real reason for her actions will, however, become obvious by the end of the story.

(d) The hospital, surprising everyone, became the center for heart transplant surgery in the region.