RE: [Bug] "You can't edit this part of the Custom buffer"

[Drew Adams]

    > Uh, are you sure this is the right thing to do? IIUC, RMS just added
    > custom-no-edit, and bound it, to raise an error when you try to edit
    > a non-editable part of the buffer.
    >
    > Simply removing the binding seems pointless. Perhaps the fix to the
    > new problem should be to better determine which are the non-editable
    > parts of the buffer, and make sure the error is only raised there?
    
    That was an incorrect fix.  `widget-keymap' defines "\C-m" to
    'widget-field-activate, which is supposed to find the widget under
    point and activate it.  It is incorrect to bind "\C-m" to
    `custom-no-edit' in `custom-mode', which inherits from
    `widget-keymap'.
    
    Why was this change made in the first place?  It seems
    pointless---Custom buffers are read-only, so self-insertion commands
    do nothing anyway; we don't have to bind them to a 'custom-no-edit'
    command that does nothing but raise an error.
    
I'm not responsible for the fix, but I reported the bug that was fixed: See the 
thread "Customize buffer modification: indicator, feedback, undo" in 
emacs-pretest, of June 10-11, 2006.