We are aware of an issue where users whom the players have muted may become unmuted when accessing the Home Menu and then returning to gameplay in an online session. Our team is aware of the issue and are investigating possible resolutions to be included in a future update. If you have any questions about this, please submit a support ticket at http://support.gearboxsoftware.com.
To be automatically notified via e-mail once more information is available, please log in to your Gearbox Software Support account and click "subscribe" in the box above this article.