One of my favorite uses for the clause comma (and there are many) is to separate an introductory dependent clause from the independent clause that follows it. The problem, as I see it, is that not every writer understands the importance of the clause comma.
I'm a big Louise Penny fan. My brother introduced me to her last summer, and I began to devour the books in her Armand Gamache series.
But alas, Ms. Penny (or her editor/proofreader) does not believe in the clause comma. When I come across one of her sentences with an introductory dependent (usually adverbial) clause without a comma that separates it from the independent clause, I'm thrown off a bit. I misinterpret the sentence. Most of the time, my interpretation doesn't make sense, so I have to read the sentence again (sometimes more than once) in order to understand. When I mentally place the comma in its appropriate place, the meaning is clear, I am at peace, and I can go on with the story.
Without the comma after an introductory dependent clause, I keep on reading without pause 'cause there's no comma to tell me it's the end of a clause! With a well-placed comma, I know that I'm at the end of a thought, there's more coming. My thinking shifts just a tad, which enables me to comprehend the full meaning of the sentence without re-reading it.