Got to agree that comment was completely irrelevant to the thread. Whatever focus the MM has on combat, or however much fluff it has for monsters, has nothing to do with it lacking an entry for 1 specific monster.
The 4E MM couldn't have a single stat-block in it, just been a collection of folk-lore stories about different monsters, and that wouldn't help TikkchikFenTikktikk if Nixies weren't one of those monsters.
For myself, while I'm hopeful to see them and similar fey discussed or statted out in the Feywild book (whenever it arrives), I'm not feeling too bad about their absence thus far. They are a rare enough creature with a small enough role in the game that I'm quite happy to have instead had more common enemies, other classic creatures, and innovative new monsters in their place.