So, is Comte-Sponville radically redefining his terms, or is there another explanation? While it's admittedly not a definitive source, I checked the dictionary that comes with my computer. Naturally, spiritual was defined as relating to the spirit (duh). So what does this dictionary mean by spirit?
The nonphysical part of a person that is the seat of emotions and character.Further definitions do refer to supernatural entities, but as you can see, this one does not. This definition doesn't imply anything about the nature of this entity. It's entirely possible that these are all brain functions or their byproducts. Actually, the word in that definition that has the most quibbling potential is nonphysical. If that word really bothers you, just replace it with intangible.
In this sense, spirit is something people deal with all the time, regardless of religion or irreligion. Yes, it refers to ethical standards, but it also refers to a general perspective on the world and how to interact with it. As you can probably guess, spirituality in this sense is of great interest to me. So the answer to the question, "Can there be an atheist spirituality?" is "Yes, definitely." You could argue that spirituality is a poor word choice, but that's an entirely different discussion.