Yep, walnut will chip off really bad. And since it doesn't have the same "body" as something like sugar maple, it is harder to carve as well.
One thing I have noticed is that carving on black walnut never looks as sharp and clean as on sugar maple, even when it is sharp and clean. I haven't quite figured that one out....
European walnut will cut much crisper and cleaner than American black walnut. But, the only European walnut wood I have is a few old Mauser stocks, so I don't get to carve it much! :grin: