In this stackapps answer there is a fairly long comment thread. As you read the comments you find that some of them don't make sense.
When you finally get to the bottom, you notice that you missed 16 comments.
I propose that you add the same 'add / show 16 more comments' button to the top of a list of comments. Or, at least, mention at the top that there are hidden comments before a user starts reading the thread.
Alternately, you could add the option to automatically show all comments by default.
Another good example are the comments on this post: Q&A sites wrongfully discourage people from thinking for themselves with respect to Q&A sites
Try reading the comment thread. You will find yourself getting lost, then you will notice that there were 10 hidden comments that could have made reading the thread much easier.