Note: This question was previously about breaking the fourth wall. I discovered that my interpretation of that phrase was wrong. I have therefore rewritten the question.
(The above is in place to explain the number of answers and comments about the fourth wall)
This question deals with an author pausing the story to speak directly to the reader. An example follows:
It is a strange thing, but when you are dreading something, and would give anything to slow down time, it has a disobliging habit of speeding up. The days until the first task seemed to slip by [...] Harry Potter and the Goblet of Fire
The first sentence is the pause in the story/narration. In the second sentence, the narration resumes. In my experience, this sort of thing is generally frowned upon by writers. The reader is there for the story, not your commentary.
That being said, I believe there are cases where this practice is fine. C.S. Lewis and E. Nesbit did it frequently in their books, and I was never bothered by it. On the contrary, I found it to only add to the story being told. I do believe that continuing to speak directly to the reader does hurt the novel, but in my experience, I've found short, to-the-point lines directly from the author to the reader only help the story. I myself have done this briefly, and my readers never mentioned it. Even J.K. Rowling does it occasionally.
All of this has led me to conclude that an author can pause the story and speak directly to the reader, as long as the passages are short, to the point, and do not overwhelm the story, but add to it.
Is this an accurate conclusion? If not, why? Please provide evidence of shared opinion.