If you decide you want to block someone while chatting, click on the three dots in the upper right-hand corner and select "Block this user."
A confirmation screen will pop up, and you can confirm by pressing "Block."
If you ever wish to unblock a user, please refer to this link for instructions: https://dreamfora.freshdesk.com/support/solutions/articles/43000716895-how-to-view-blocked-accounts-and-how-to-unblock-users-
*Please note that unblocking cannot be done within the Chatting feature. Also, be aware that (un)blocking someone in Chatting and within the Feed are interconnected.