I think this is a very good move for Patchou, as most people who use Messenger Plus! like to have fun (which is why Messenger Plus! exists, in the first place), and sounds are a great form of fun and interaction.
With the possibility to record your own sounds, you can actually record funny things and send them to your friend. And if that friend is not using Messenger Plus!, then you will recommend it to them, and thus more users will get Messenger Plus!.
Well, that's my rant of the day.
Stating the Obvious 
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