Changing a comment shape

To change the shape of a cell comment, add a command to your Quick Access toolbar (see Adding commands to the Quick Access Toolbar):

   1.   To the right of the Quick Access toolbar, click the tiny arrow button to open the drop-down menu:

   2.   Near the bottom of the menu, click More Commands....

   3.   In the Excel Options dialog box:

• From the Choose commands from drop-down list, select Drawing Tools | Format Tab.
• From the list on the left, select Change Shape and then click Add >>:
  

   4.   Click OK to close the Excel Options dialog box.

After performing these steps, your Quick Access toolbar has a new Change Shape icon:

To change the shape of a comment, do the following:

• Make sure that it is visible (right-click the cell and select Show/Hide Comments).
• Click the comment's border to select it as a Shape (or, Ctrl-click the comment to select it as a Shape).
• Click the Change Shape button on the Quick Access toolbar and choose a new shape for the comment:

See also this tip in French: Comment changer une forme de commentaire Excel.