The glasses means you are subscribed to the thread and you will be notified when someone posts in the thread. Since you are trying to sell something, it's a good idea to be subscribed to the thread.
If you don't want to be subscribed, click on the thread go to the top and there will be some options. Look for watch thread and change that setting to unwatch thread or no longer watch the thread - whatever it says. Then, you won't be notified when someone posts on the thread.