While I think the intentions of the voting system are for marking low quality, as you've said, I think in practice most downvoters are using it to mark their disagreement.
There's something interesting about that; it implies that grey text signifies a non-conformist view and approach to a technical issue. As is the case here.
I wrote the downvoted comment and am a proponent of downvoting for disagreement. Downvoting is an alternative to arguing and often makes for better comment pages.
