excel – Moving the left-popping comment to another column can make it pop right, as can modifying the comment's contents

The comment boxes are stored as shaped within the comment within the cell.

This code will control the pop up direction in relation to the active cell it is stored inside of.
(assuming a comment in cell D8)

Sub MoveCommentLocation()
    Dim x As Integer
    Dim y As Integer
    Dim bVisible As Boolean

    With Range("D8")
        ' read position of the cell
        x = .Left
        y = .Top
        ' if comment is initially hidden, we need to unhide it to move it
        bVisible = .Comment.Visible
        If Not bVisible Then .Comment.Visible = True

        With .Comment.Shape
            ' move comment relative to the cell
            .Left = x - 30
            .Top = y + 50
        End With

        If Not bVisible Then .Comment.Visible = False
    End With

End Sub

Note:
You need to unhide the comment before moving it if it’s hidden. (code included above)

Additionally, Excel chooses the closest corner of the comment box to the top right of the cell to chose where to draw it’s arrow. If your comment boxes will vary in size/shape due to context and font I’d suggest placing them to the bottom right of the cell so that the location will always have it pointing to the top left.