I assume moderators disable comments (automatically or manually) on such dummy posts because they usually don't contribute to the conversation, such as by posting just "thank you" or some comment about the article that'd be better suited as a top-level comment

(Not that I necessarily agree with this practice. Don't decapitate the messenger)

There wasn’t one, I took a screenshot to make sure I wasn’t missing it. It was the newest comment by krunck that had the button missing.

It does seem to be missing from individual comments on rare occasions. I've assumed this to be a bug in the past. Maybe refreshing helps?