I have thirty-eight years experience teaching in public and private schools. Though history, economics, English, and civics drove the content everything required extensive writing and proofing of both my own material and student submissions. I've done my share of proofing and editing at all levels of competence. I like good literature and know when something needs to be massaged regardless of the particular content. The areas most people need help with include awkward or confusing sentences, poor grammar, redundancy, and inadequate vocabulary or misused vocabulary. Editing other peoples' errors is akin to identifying pornography. You can't explain it, but you know it when you see it.