A couple of things pertinent to the "writing group" experience.

Why do people, when they're reading for response, indicate words they didn't know? Either with a circle or a question mark, or a "huh?" penciled in the margin. If they think the word is used inappropriately that's one thing, and I would expect them to comment, but the comment - it seems to me - should include some notion of what they think the "correct" (or at least "more commonly expected" usage should be). But usually it's pretty clear they're saying "hey, I don't know this word." Perhaps it's just a quirk of mine, but when a writer introduces me to a new word, my response is usually "Thanks! great new word for me!" or so. I'm eternally grateful to S.J. Perelman and P.G. Wodehouse for enriching my vocabulary immeasurably. I can't go three pages in either of them without learning nifty new stuff.

And why do people correct dialog (except the spelling of words clearly not intended to be rendered phonetically, or placement of punctuation & quotes, etc.)? Or comment that this or that phrase "wasn't necessary" or "he just said 'indeed' two sentences ago..." - well yeah, he did, because that's the way he talks. It's a little like reading "He was wearing a brown fedora" and writing in the margin "I don't care for that shade of brown."