I really wish goodreads would add a site map, there are too many features on the site to not have an index. There is a help page – accessible from the bottom of every page and from the profile drop down menu. The blog announces major changes, but smaller changes are made constantly.
To find all the features of a page on goodreads, you have to hover over everything and click on anything that is clickable. It’s not always obvious what a link will do, so try everything. All of the words at the top of the screen are clickable links that lead to pages that are different from the links in the corresponding drop down menus.
On a group post, if you click on a person’s name, it will show you all of their comments in that group. If you click on their picture, it will take you to their profile.
If you can’t find something, just ask in the feedback group. You could try searching in the feedback group, but the search in discussions can be frustrating, but hopefully they will make some improvements eventually.