Is it ever worthwhile to de-quirk a novel?Yes, sometimes it is worthwhile to revise this sort of thing.
My book has one seriously odd character: a home-schooled narrator. The consensus among replying agents, however, is that the voice is just too "quirky". Fair enough, but now what?
Is a complete re-write in order? And a re-query to follow?
Or should I trash the manuscript, hit the bottle, and move on?
Quirky can be great-- it can mean charming, funny, unique. But "too quirky"... If you're getting a lot of this feedback, I would start to wonder if what the agents really mean is weird and distancing.
The right amount of quirky reminds people of themselves, their own uniquenesses. Too much, though, and you can lose your audience, especially among kids, who can be pretty judgemental about weirdness in others.
Still there are good examples of very unusual behaviors and world views that absolutely work for the book they're in... Because the author has taken the trouble to make them make sense for that character-- to show us why they have these quirks.
I would suggest that you ask yourself which of your character's quirks are serving the character development enough that it's worth going to the trouble of showing the reader why the character has those quirks... and which quirks you maybe just added for "flavor"-- as a shorthand for character development. I have a hunch that some of those quirks just aren't earning their keep in your story.