As I said at the start, I'm intrigued by this reform, and kudos to Beaudrot for raising it and Yglesias for adding to the thought. I really want to support it. As I said, the intuitive case for it seems, to me at least, to be pretty strong. Another way to look at it is that we've really had a major reform in representation by massively changing the size of House districts over the last hundred years, and when we have those kinds of accidental reforms it's a real good idea to think them through.
There's one more reason for reform here that's worth mentioning, which is that it would almost certainly be very good for some forms of demographic diversity. Especially women in the House: add a thousand new seats, and you're almost certainly going to significantly increase the percentage of women in the House.
But overall, I just don't see that the gains are worth the downside. I want House elections to have more visibility, not less; I want Members of the House to be serious legislators, not cranky back benchers or opportunists looking to cycle through for a couple terms and then parlay their House career into lobbying or talk show host careers. Those are serious consequences, and they override the possible (and mostly speculative, at least on the representation side) positive effects.