I think it signifies your *attitude*. Emotion by my interpretation is mostly influenced by water (inward emotion) and fire (outward emotion) in your chart. The moon signifies your attitude: how you think about your emotions, how you direct your emotions, how you *reflect* on your emotions, but not what emotions you feel or how deeply you feel them.
This is just kind of a hot take from observations and self evaluation. I often see people define emotions by their moon sign which does not track from my anecdotal knowledge. The moon is always, to me, about your natural reaction to those emotions but never an embodiment of emotion itself. Hence why I’m suggesting it’s your attitude: it’s a reflection, not the object being reflected. I find this to be very appropriate for the luminary whose basic nature for us is to reflect the sun.