Simple, declarative sentences are not necessarily better than complex ones; the converse is equally true.
Clarity is a desideratum, but it is not necessarily a bad thing to challenge the reader.
Loose verbiage is not a hallmark of good writing — pruning is desirable; but, shorter is not always better. (Nor is the most concise style a prioi the best one.)
Objectivity and balance are often desirable, but not at the cost of dullness; the opposite, a fulsome, over the top, raging screed, is usually not worth reading.
Subtlety and irony can be as desirable as making one’s point bluntly and forcefully; it depends.
No argument can stand on its own without support by way of evidence, details, illustrative examples, etc.; and, explication.
Vagueness and fuzziness are to be avoided; but abstractions and abstract words do not, per se, amount to the same thing.
It is not necessarily a fault to digress, or to yoke disparate topics in a single piece. (But one should avoid the possibility of the reader getting lost or confused.)
Speaking directly to the reader and/or making an abstract argument more personal are not “wrong.”
Draw upon your own experience where appropriate.
Sentence fragments can work, if used sparingly, in the right place (but not abused).
Punctuation should not be dispensed with merely for the sake of convenience.
Comma splices are almost always an avoidable and unjustifiable error.
Adverbs can be overused, but they are not necessarily “bad”; it depends. (The same can be said for adjectives.)
Vulgarity is almost always a mistake.
Connectives such as moreover, however, and on the contrary are essential and desirable for coherence, but they can be overused; coherence can often be achieved in more subtle ways.
Filler words and qualifiers such as as it were and so to speak can often serve a purpose.
Emphasis is key; it is not always or merely a matter of putting the key idea at the end.
Time honored grammar rules should be heeded and not ignored simply out of ignorance or on account of laziness or political correctness.
Fifty cent words are not verboten; recherché words and foreign terms should not necessarily be shunned.
Clichés are not always bad.
Good writers are allowed to break the rules, but first they must know them.
— Roger W. Smith