It feels like this comment was almost a purely additive anecdote of your own experience with a similar kind of issue, but you've spoiled it by deciding to tell the author that they're incorrect about how they felt during the process?
Maybe different people find different things fun.
Not saying he's wrong, sometimes the word "fun" connotes something slightly different what what it literally means. "Satisfying" is something I'd use for the end state. Maybe "challenging" for the intermediate state. But while you're in a high-pressure situation that you don't understand, that is rarely "fun" in the literal sense.
You wouldn't pay to be given compiler race condition bugs, right?