You can reply directly to the latest parent comment, underneath an item of content on the mobile social feed.
You can like the latest parent comment under an item of content, by clicking the Like icon on the comment. 
To reply to the latest parent comment:
- Tap Reply underneath the parent comment.
The Reply to [User name] field appears. - In the Reply to [User name] field, enter your reply.
- Tap the Send icon.
- Your reply is temporarily posted below underneath the parent comment.
Once posted, your reply is only displayed temporarily. If you refresh the feed, it is hidden.