What are the current penalties for leaving a casual mode game early?

As the title states, what are the penalties for quitting a game early in casual mode?

Do you get any experience added to your level if you leave early?

This patch note (released on June 22, 2016) states that:

Abandon penalties have been removed, which means players can come and go as they please.

It looks like the actual update that removed the penalties was on July 8 2016.

The patch notes also state that:

Right now, leaving a casual match results in no experience being earned. We are looking at changing this to avoid penalizing players for having to leave after investing significant amounts of time into a match, while still providing rewards for playing matches to completion.

It looks like they held true to their word, because an update released on September 27 2016 made it so that you will keep your XP if you leave a casual game early. As they worded it:

XP is no longer lost for leaving a Casual match early.