Stef maybe you mean this:

http://lists.squeakfoundation.org/pipermail/squeak-dev/2005-May/091256.html

On September 17, 2005 13:22, Stéphane Ducasse wrote:
> Hi all
>
> I cannot find anymore the email where it was mentioned that Morphic
> got a slow down
> after refactoring some == nil into isNil or related.
> I would like to know whether a cs has been made that I look at it for
> 3.9a.
>
> Stef