As far as incomplete constructions, they are wrong. About repetition, the repetition of a word might be real effective repetition - take, for instance, the repetition of Abraham Lincoln. In my opinion, I think that an author, when he is writing, should definitely not get into the habit of making use of too many unnecessary words that he does not really need in order to put his message across. Use parallel construction not only to be concise but also clarify. It behooves us all to avoid archaic expressions.
Mixed metaphors are a pain in the neck and ought to be weeded out.
Consult the dictionery to avoid mispeling. To ignorantly split an infinitive is a practice to religiously avoid.