***** NOT A TEACHER *****
You have asked a very difficult question. I do not have the confidence to suggest an answer. I do wish, however, to present
some ideas -- and let you decide for yourself.
1. One book * says this:
"Never supply anything that is not absolutely demanded for grammatical completeness."
That book gives this sentence: "He went up the stairs and knocked on the door."
The book says that if you supply a "needless" he, you turn that simple sentence into a compound sentence.
The book feels that "the author of that [simple] sentence never intended" for the sentence to be a compound sentence.
2. Another book ** gives these sentences:
a. "I met Frank at the parkway [freeway/ autobahn, etc.] and I found the car waiting there." = compound sentence.
b. "I met Frank at the parkway and found the car waiting there." = simple sentence.
3. This same book gives this simple sentence: "John and Mary enjoyed the performance and applauded it wildly."
a. The book does not like that sentence. The book thinks that the second part of that sentence is "an independent
consequence" of the first part, so the book suggests a compound sentence: "John and Mary enjoyed the performance,
and they applauded it wildly." [NOTE: the comma is MY idea.]
4. Finally, a third book *** gives some sentences. Do you think they are identified as simple or compound? I will give you the book's answers later:
a. We sang and danced all night.
b. We fished all day, but didn't catch a thing.
c. The hotel was cheap but clean.
Answers: a) simple. b) compound (the word "we" is understood). c) simple.
I have not expressed any opinions. I have just presented evidence from the experts.
* R.W.Pence and D.W. Emery, A Grammar of Present-Day English (Second edition), page 152.
** John B. Opdycke, Ph.D., Harper's English Grammar (1987 paperback), pages 232 and 247.
***L.G. Alexander, Longman English Grammar (1988 impression), pages 10 and 12.