This was part of the opening post on a thread in the US forums, discussing the Community Management team's choice of posts to respond to. And it's a reasonable question, a cursory glance at a blue tracker will reveal that many blue responses are indeed on light-hearted threads rather than on the ones demanding feedback on heavy issues. That, or they're commenting on quickly locked posts that violate the forum guidelines, elucidating the reasons for the thread's closure.
"Why do the blues only seem to comment on silly threads and never in a thread that has substance, provides meaningful insight, or merits actual discussion? This seems a complete waste of time and valuable resources."
Why don't the blues respond more quickly to the weighty, substantial threads? Consider the amount of work required in the background to respond to a question about PvP balancing, for example, compared to the amount of work required to wish a forum a happy Winter Veil. While the latter simply requires a lively wit and a good knowledge of the forum code of conduct, the latter requires a good deal more input, from the developers and designers and more.