Great points. What about the spammy comments where the person (or bot) says something totally unrelated to the post in an attempt to drive traffic? Like in response to this post I might write “I stumbled on this blog and I love your content, especially the article about how to roast a turkey. I will definately be back!”
In all seriousness, this makes me feel less bad about the bad job I do of commenting on other folks blogs. It’s nothing personal, just time constraints and pure laziness.