Context is everything. I agree with this point. Context is very important online, especially with family and friends.
Double-check before you hit "send." This point I know firsthand from seeing other people get into arguments they could avoid, and myself getting into a loud dumb Youtube argument once.
Take the high road (but don't boast about it). This one conflicts me a little more, as flame wars are fun to get into every now and then. Still, one might want to avoid them, so this rule does often apply.
Grammar rules. Idiots who cannot use grammar or spelling online are always the funniest. I once chatted with a person who couldn't use proper spelling or punctuation while he ranted against improper grammar use. Misusing grammar online is acceptable, but if one cannot actually use the English language to a certain point, they will come off as an idiot.
Keep a secret. This one is another good point. Avoiding posting personal data, or as the article says, something that can spark drama, is a very wise choice indeed.
Don't hide. Anonymous people generally tend to be harmless, but they are too often trolls. Anonymity can come off as an attempt to troll, so yes, one should avoid anonymity.
Remember the Golden Rule. This one I don't agree with. While face to face etiquette is definitely based around this rule, online etiquette is much different. Generally people who are very sensitive online will sign off at sudden harassment, and only be truly bullied if it continues. Without face-to-face interaction, there is no real need to be super polite. Online, people don't need to follow the golden rule. If they did, it would be a very boring place.