Cheesehead was the one who originally exposed me to the "blogstone" so I have to blame her. Whether she is the one who made it up or not, to me, she is to blame.
A blogstone looks like this (o) or (O) or (0) and is not usually accompanied with anything else.
A person would use a blogstone when reading a post and you really don't have anything to say or maybe you do not have enough time to write what you want to say for the comment. This is the easy way to signify you were there and read the post. Sometimes that is enough.