You can use the following piece of Javascript as a bookmark in your browser to expand all the comments and threads in an Asana task. This is really helpful when you have long threads with lots of comments and you are unable to see all of them because Asana hides them by default.
Copy the code from the Gist and paste it into the URL field when you create a bookmark in Chrome or FireFox.
When you are on a task in Asana and want to open all the comments and thread, just click the bookmark that you have created in either bookmarks or your bookmarks bar in your browser.