How to change the feed placeholder text on my sites?

This has to be done by Site Managers or App Managers.

To change the feed place holder text:

1. Click on your avatar at the upper right hand corner, go to "Manage Sites".
2. Select the site from the "Select for a Site to manage:" field, click "Manage".
3. Go to the "Governance" tab.
4. You can change the text for the feed in the "Custom Feed Placeholder Text" field.

"Site Feed placeholder text:" refers to the main feed that appears on the site feed page or the Site Dashboard.

For the "Site Feed placeholder text", you can use #name#, #userfirstname# as the placeholder.   

#name# is a dynamic text. The name of the site will appear in the feed.
#userfirstname# is the first name of the user.

"Content Feed placeholder text:" refers to the feed that appears under the content, such as site pages, news, events, and albums.

You can use these three tags:
#type#, #title#, #userfirstname#    

#type# -> Content Type eg. News/Page/Event/Blog/etc.
#title# -> the title of the content