There Are No Missing Comments
You see 2 comments and click on them, and get nothing. Or you see 3 comments, click, and only get two.
The problem is due to a rather poor choice made by the developers to use the comment part of the database to record up and downvotes. (I up and downvoted things to confirm this.)
I see this consistently on questions, but not on answers. (If you see it on an answer please let me know!)
So it’s annoying, but you’re not missing anything!