OK, so they had discussion, covered their mouth and both looked adorable, calm... what did they talk about?

Or:

"Against me you always s*** yourself," said Pepe.

prompting the incredulous reply from Messi:

"What are you talking about? I always score against you! Thanks to me you are always end up in the pictures".

It's pretty hilarious :)

You forgot to put the link in.
http://bleacherreport.com/articles/2005068-lionel-messi-and-pepes-clasico-conversation-revealed-argentine-trolls-opponent

Is this true?

It's not true. Just rumors. No doubt they were both cussing at each other, but they had their mouths covered by their hands, and none of their words were audible.