You can reply to the latest parent comment under an item of content, directly in the mobile social feed.
You can like the latest parent comment on an item of content, by clicking the Like icon under the comment. 
To reply to the latest parent comment under an item of content:
- Tap Reply underneath the parent comment.
The Write comment... field appears.
- In the Write comment...field, enter your reply.
- Tap the Send icon.
- Your reply is posted below the parent comment.
If you navigate back to the social feed, your reply is hidden from view.