Benefits of "Mental Noting" during positive events?
I spoke before about the power of narratives. Narratives is how our mental world is shaped, narratives is one of the main ways to control the sukha/dukha mechanism described in the Four Noble Truths.

In this case, mental noting is a special case of narrative. By looking at thoughts and emotions in a certain way ("in and off themselves" as Buddha said in Satipatthana) we create a special philosophical narrative in which the thoughts are things of a different order than they are in our regular everyday context. We look at them neutrally, philosophically. Hence the dissociation effect.

However, mental noting is just one way to do narrative. The idea is to be the master of your thoughts (via control of the context / frame of reference) instead of being driven by your thoughts (being locked in a certain context). So don't fall in the same trap with your positive experiences, you don't have to shape it in a way that does not induce positive states of mind. You are totally free to create any sort of narrative (assuming it is true, not harmful, and does not go contrary to Dharma) - as long as it drives you up. In fact the whole point of the First Jhana is to learn to control your mood via narratives (and then directly, in the Second Jhana).