I'm guessing it was flagged because it came off as snark. I've gone ahead and vouched it but of course I can't guarantee it won't get flagged again. To be frank

I'm guessing it was flagged because it came off as snark. I've gone ahead and vouched it but of course I can't guarantee it won't get flagged again. To be frank this comment is probably also going to get flagged for the strong language you're using. I don't think either are abusive uses of flagging. Additionally please note that I neither complained not expressed an entitlement. The author owes me as much as I owe them (nothing beyond respect and courtesy). I'm just as entitled to express a criticism as they are to publish a book. I suppose you could characterize my criticism as complaints, but I don't see what purpose that really serves other than to turn up the rhetorical temperature.