Why would you want to do that? Could you provide some example subtitle-comments? Are they things like "I wrote this poem in only 10 minutes, so, whatever," or "I wrote this about my grandmother when she died," or "the fire hydrant represents what C.S. Lewis might term between the Angel and the Animal in humankind"? Don't you think the poem should say those things by itself, or be able to do without them? More to the point, don't you think that's just kind of sad?