These are good guidelines, I generally agree with all them (and I've messed up tons of times as well). It's important to note that you should write comments for the developer, whoever that is. That means understanding their perspective, their experience, and what they want.

Some developers really won't take offense to many of the "bad comments" suggested, and could even feel patronized if you take some of the guidelines - for example, over explaining something could be overkill for someone who just made a mistake.

I've also found that taking a lighthearted approach to code reviews really lightens up a stressful interaction. Simple jokes, comments like "dead code! woo!", and whatnot make a difference.

And lastly - don't forget positive comments!! Celebrate people's work when you can!!