1. Give id's to comments so we can #reference them (I looked for it but didn't find it, surprisingly).
2. Add a "parent" link to each of a comment's children, referencing the aforementioned id, so that it's much easier to locate the parent of a comment when it's offscreen because there are lots of replies. To peek at the parent we'd just have to click the link then hit the browser back button. Perhaps use some javascript to make this parent link appear only when the parent is offscreen.
3. When we post a reply use the anchor in the obvious way so we don't have to find our comment manually. Usually you want to continue reading the comments after the one you just posted.