Why am I not seeing the Chatter "Mute" Option?
|Knowledge Article Number||000229937|
|Description||Chatter Mute is enabled by default in all new orgs and in some existing orgs. This feature is available in Salesforce Classic only.|
|Resolution||If the Mute feature isn’t available in your org, contact Salesforce and we’ll enable the feature for you.
See also Mute Posts for more information.