Whenever I get a comment that is from Anonymous, I always wonder. Most times, Anonymous simply means that someone has something nasty to say, but they don't want to take responsibility for it so they don't sign their real name. I guess if I really cared, I could trace back their DNS and find out who they are. But I'd have to care enough, which I don't.
Most the time, their comments are just nasty and undirected toward any of my posts. The person just feels like saying something nasty or profane.
My advice to other blog masters that get these remarks is to just not worry about them. It's the reason why we have our blogs set to moderation, to keep out the riffraff. It truly isn't a response to what you've written. In Internet parlance, these people are known as trolls. Don't feed them.
Then there are the other letters that are signed by Anonymous. They are written by people that have interesting things to say, but don't want to use their names because the subject or comment is too personal. It might hurt someone if names are used. I prefer to have people use their name, but I do understand.
I guess that is the lot of having many readers.