If you look in the SCJP - Coaching centres in Pune topic, you can see that vishal bahedia was the original poster (in other words, he was the person who created the topic). Therefore the icon appears next to every post of his in that topic. It does not appear next to your posts in that particular topic since you were not the person who created that topic.
It may be a minor thing -- as you can confirm who the OP is simply by scrolling -- but it is useful. Sometimes, you can have a long discussion in a topic, elaborating deeply on a question with a user. And not realize that you are not having the discussing with the OP and actually detouring the topic from the original question.