Try this manually:
Find a comment that looks bad.
Rightclick on that cell and select Edit|comment
Now click on the comment's border
Format|Comment
If you only see one tab (Font), you missed the border.
If you see a tab named Alignment, select it.
Now check the "Automatic Size" box.
(Ok your way out.)
Did it look ok?
If yes, then you could have a macro that fit them all.
Open a new workbook (where we'll store this macro)
Save it as: FixComments.xls
hit alt-F11 to see the VBE where macros live
hit ctrl-R to see the project explorer (like windows explorer)
Look for VBAProject (fixcomments.xls)
Right click and select Insert|Module.
Paste this into that new window that just opened.
Option Explicit
Sub AutoSizeComments()
Dim cmt As Comment
For Each cmt In ActiveSheet.Comments
cmt.Shape.TextFrame.AutoSize = True
Next cmt
End Sub
Hit alt-Q to close this and go back to excel.
Save this workbook with your new macro.
Open your workbook that has the worksheet with all the comments.
Go to that worksheet.
Tools|Macro|macros...
look for fixcomments.xls!AutoSizeComments
select it and click Run.
Whenever you need to do it again, just open that workbook and
tools|macro|macros...