inline comment delimiter

I'm having a little trouble getting inline comments to work.
According to the manual, "Anything on any line following a quote is
ignored.".  But the manual doesn't say whether to use single or double
quotes.  From experiment, it seems that single quotes work on most
lines, but double quotes work on a .SUBCKT line.  Here is a test
script:

*Comment test
*On a .SUBCKT line, it seems that " is a comment delimiter
*But elsewhere it seems that ' is a comment delimiter
.SUBCKT Foo 1 2 "(IN
*This next line will not work if you uncomment it
*.SUBCKT Bar 1 2 '(IN
.ENDS Foo
R  1 2 1000
D1 2 0 DIODE1 ' a comment
V1 1 0 dc 1 ac 0
.MODEL DIODE1 D(IS=8.2592e-16 RS=10) ' a comment
.op

Can someone clear me up here?  I'm working on a tool to automatically
convert LTSpice models into Gnucap models, so 'just change it by hand'
isn't a viable solution.  I need to be able to choose the right
delimiter in all cases.

-Alan Somers