My most recent attempt seems to be working fairly well. What I am
doing now is to preset the font to Arial Bold Italic 10 and use a 90
character line cut-off, which is a couple of characters short of the
total line space, and then increase the height by 15 with every
additional 90-character-increment. I'm hoping that allowing a
couple characters leeway for each line will allow for the
proportional font.
I'll have to ask the supervisors if it's going to be enough,
but I increased the limit to 270 characters which is 3 total lines.
If they say it should be more, I can keep going, of course.
Initial tests showed it to look pretty good. The code is very
simple, and in fact a lot simpler than I expected:

Dim comlen as integer
comlen = Len(ActiveCell.Value)
Range(Cells(nxrow, 1), Cells(nxrow, 6)).Select
With Selection.Font
.Bold = True
.Italic = True
.Size = 10
End With
If comlen < 91 Then
Selection.Rows.RowHeight = 15.75
ElseIf comlen < 181 Then
Selection.Rows.RowHeight = 31.5
ElseIf comlen < 271 Then
Selection.Rows.RowHeight = 47.75
End If
'then the code goes on to merge cells,
'and add a border to set the comment off
'from the numbers

They are telling me that it's rare to have that long a comment,
so I'm hoping that the formatting  will fit for 99% of the cases.