It could sound trivial, but a simple note feature can become a powerful tool to combat hindsight bias. The Notes feature allows you to attach a note to anything: a stock, your account, an opinion, or a strategy in the Research section. All the annotations that you ever made are shown in the general notes page where you will be able to edit and search them. You can access the general notes page by clicking the squares icon:
Stock notes are unique in the sense that they are "global". No matter where on the site you added a note about a stock, it will be visible whenever the stock is shown. Stock notes are also visible on stock charts.