How about resizing them when you're done via a macro?

http://www.contextures.com/xlcomments03.html#Resize
(From Debra Dalgeish's site)

wrote:

Rather than selecting the "Automatic Size" for each cell
comment ONE AT A TIME, is it possible to set your options
so that all cell comments start out with the automatic
size feature enabled?
Thank you.

--

Dave Peterson