I love racing in the rain, it's a hoot! I just don't like getting cold so make sure you have the appropriate riding gear. You won't have any fun and you'll go slow if your fingers and toes are wet and cold.
I've never been a big fan of putting my foot on the ground, even off road (where I've caught it on things). It just seems like a recipe for a broken ankle. If you're comfortable with it then it's problably not an issue either way. If the bike steps out, it'll step out. Having good smooth throttle control is more important than whether you have your foot down or not.
You also want to make sure you stay on the racing line. That is where the water will (generally) have less pooling and you'll have better grip. If you get off the line you'll have to deal with debris and oils leaching out of the pavement.