As stated above, the juice that comes out of the cherries during cooking is not added to the batter, but you can reheat this to serve with the clafoutis, leaving your guests to pour it over. You can also add it to whipped cream to make a cherry chantilly.
An interesting variation: leave out half the flour and replace it with chestnut flour or ground almonds.
Cherry stones: should you leave them in or not? I've discussed this at length with Isabelle (my favourite sister) and there's no easy answer. Personally, I hate eating a clafoutis with the stones in - I'm always worried I'll break a tooth. You need to be very careful when eating it!
Untl recently I thought that leaving the stones in improved the flavour, but I ended up trying a clfoutis with stones and one without, and... no noticeable difference.
I think the Kirsch adds the subtle flavour of cherry stones, and this is better than leaving in the stones themselves. If you really want to keep the taste, you can try the following: bring the milk to the boil with the crushed cherry stones. Leave to infuse for 15 minutes, then strain and continue the recipe as normal.