The new Moto G has an issue where emoticons do not show in any application correctly – where they should be is a blank space. This ‘bug’ has been shipped with the phone, but it is a misconfiguration left in by the developer and is easy to fix.
Go into the stock messaging app (not hangouts) and enter the settings. Find the ‘Character Encoding’ setting and change it from ‘7 bit’ to ‘automatic’.
This configuration seems to be a system-wide settings, and all applications will now display emoticons successfully.