I'm with halley. If you find some real gems buried in the deeper reply chain below an otherwise lousy top-level node -- and especially if you can elaborate a bit on what you think is valuable in the sub-threads (why you feel compelled to draw wider attention to those replies) -- start a new thread to highlight those gems.

If others agree, there's a good chance your "commentary" node will be frontpaged (and you'll get all those lovely ++votes).

I'd also look at it this way: as often as not, someone who posts a poor top-level node does so out of innocent ignorance. Maybe they'll grow out of that someday, so in the meantime, why front-page their lousy OP question or whatever, and expose them to an amplified downvote reaction? It wouldn't be fair to them, nor would it generally benefit the site as a whole (having stupid questions on the front page... bleah.)