SO is distinguishing between replies which are comments and answers.
Yes, SO has a very strict format, sometimes stiflingly so. Although the original SO site isn't that bad, I'm a regular on a number of other StackExchange sites where people are regularly admonished "don't post answers as comments" and any comments which don't strictly fit the purpose of "helping to improve" the question/answer they're attached to are rapidly deleted.

In reply to Re^3: Unanswered Perl questions on Stack Overflow by dsheroh
in thread Unanswered Perl questions on Stack Overflow by davies

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