Hi,

currently, the design allows Edit/Delete actions only to owner of the message board, and also those who are authorized to manage messages (Modify permission for Message boards module). However, that permission allow to modify all messages, which is probably not wanted.

To override the default behavior, you could modify the Message board webpart, which renders the messages and decides to show the Edit/Delete controls.
It can be found in ~\CMSModules\MessageBoards\Controls\MessageBoard.ascx.cs, particular code is:

// Handle buttons displaying
boardMsgActions.ShowApprove = ((this.BoardProperties.ShowApproveButton) && (!bmi.MessageApproved) && userVerified);
boardMsgActions.ShowReject = ((this.BoardProperties.ShowRejectButton) && (bmi.MessageApproved) && userVerified);
boardMsgActions.ShowDelete = ((this.BoardProperties.ShowDeleteButton) && userVerified);
boardMsgActions.ShowEdit = ((this.BoardProperties.ShowEditButton) && userVerified);

You could add a condition to check also if the current User is a friend of the Message board owner. Would this be a solution for you?

Should you need any additional details, feel free to ask.

Regards,
Zdenek C.