Removal of a contact from messages favorites

You can accomplish that by removing the entire message thread with this contact from the Messages app. NOTE: All of the messages exchanged with this contact will be deleted from the Messages app, however, their contact information will remain in the Contacts app.

Open Messages app ➡️ Touch and Slide the Message Thread to the Left ➡️ Tap on Delete Button revealed to the right.

Axel F.

There isn't a way to hide conversations in Messages without deleting the entire conversation.