Everyone was a network newbie once. And not everyone has had the benefit of reading this book. So when someone makes a mistake — whether it’s a spelling error or a spelling flame, a stupid question or an unnecessarily long answer — be kind about it. If it’s a minor error, you may not need to say anything. Even if you feel strongly about it, think twice before reacting. Having good manners yourself doesn’t give you license to correct everyone else.
If you do decide to inform someone of a mistake, point it out politely, and preferably by private email rather than in public. Give people the benefit of the doubt; assume they just don’t know any better. And never be arrogant or self-righteous about it. Just as it’s a law of nature that spelling flames always contain spelling errors, notes pointing out Netiquette violations are often examples of poor Netiquette.