I went in there last week, in person, to make a reservation for the end of next month... and she very tersely told me "We are booked through December".
I called for a dinner reservation when I arrived in Paris the beginning of September and was told they were booked through October 3. Did they have a list for cancellations, I asked? It is to laugh, I was told, essentially.
Walked by one lunchtime and Monsieur C. himself suggested we come back in 20 minutes. Thirty minutes later we were eating some yummy pied de porc. It became clear that if you arrive somewhat before noon they will seat you and let you wait until they begin service at noon, or if you arrive after 1:30 you will have a minimal wait for a table. As the weather deteriorates this may change, since the outdoor tables will be unavailable.
I really liked the food and wouldn't deprive myself because of a snooty reservations clerk, but that's just me. I'm happy to have a lovely long lunch if I can't have dinner. Dinner at La Regalade several weeks later was also fabulous, but Le Comptoir is more accessible to the area I stay in.
By the way, what's with all the "verrines" of food? Saw this both at Le Comptoir and at Aux Marches du Palais, where we had another enjoyable lunch.