When viewing individual comment trees, usually by opening a comment from my own history that has replies on it, or just clicking view context: the original comment is the furthest indented, with the replies indented one less, and further replies to those less indented still until the lowest level comment appears as the oc, but at the bottom of the list.
Here’s an example:
Those links came from a kbin user asking about their ‘share link to Fediverse’ button. I was just checking if either would happen to open here. (they posted them as non hyperlinks so I had to repost them to find out)
Was just an example that’d actually fit on screen.