Shorter sentences work better. In the 'American method', at least. Albert Camus wrote the first half of The Stranger this way--precise and briefly. You can see how in the second half of the book, he changes up the style again to better illustrate the inner world our protagonist has retreated into. But it's important to change things up in your writing. If you keep things running on too many times in a row, you'll lose the reader. Each paragraph has its own cadence. Longer sentences aren't any smarter or more adult than short ones are. Probably less so. When I write, sentences always goes from short to long. Then from long to short. And once I'm sure the reader is well-rested I can hit them with a sentence that stretches way out passed its due date, and maybe it even continues with a comma splice. Tell him/her to read their work out loud. The awkward and breathless comma splices will make themselves much more apparent.
To me, shorter sentences are great for punctuating a point, but they can really lack depth at times. The other day, on another post, I mentioned a sentence I had to study in detail in college that my instructor held as the greatest sentence he was aware of (I learned a great deal from studying it). This sentence, while not overly long, has seemingly infinite depth; it would be impossible to recreate its appeal with several sentences that purport to convey the same information. Each modifying clause adds another layer to the initial, simple sentence, and each clause is even successively more complex, the first being plain vanilla, the second inventing a new word (fatly), so that we may envision in our heads what Faulkner even means by "fatly earnest", a phrase that none of us has ever heard, but that we can intuit immediately, the final using a very delicate metaphor, beautiful yet precise. Simplicity just would not do. Anyway, I guess my point is that variety is the most important thing. One needs to know when to use subtle, complex sentences, and when to use the blunt force of a short sentence.Shreve was coming up the walk, shambling, fatly earnest, his glasses glinting beneath the running leaves like little pools.
Your instructor is right, that sentence is dope. And you're right too, adding clauses isn't always a bad thing. The semicolon thing is right, too, but I think it's easy to overdo it with those. I guess I come from the minimalist school of thought. But I think the important lesson here (as we've seen with all the different viewpoints and what kleinbl00 said about 'correctness' in our language) is that it's important to switch it up, as you said. Damn, I'm just reading through all these replies. Punctuation and grammar just set this place off.
Yeah, in the Translator's Note in my edition the guy talks about how Camus acknowledged employing this 'American method' in writing the book. "the short, precise sentences; the depiction of a character ostensibly without consciousness; and, in places, the 'tough guy' tone." Kind of interesting, but I wonder why.