escaping 'comment' chars in example sections

Dear list,
I've noticed that, when writing examples in an Rd file, you need to
escape the '%' character, even if it is valid R code.
I can see maybe this is the intended behaviour, but I found it a bit
surprising, and leads to cryptic error messages from 'R CMD check'.
The relevant section in the "writing R extensions" manual isn't clear
on that point either.

To reproduce the behaviour I'm talking about, you can run this snippet:
##
library(tools)
Rd2ex(parse_Rd(textConnection("
\\title{a}
\\name{b}
\\examples{
'a' %in% letters
}
")))
##
You can see that everything from '%' on is dropped from the output, as
a regular Rd comment. Should this be mentioned in the manual?

cheers,
fabio.

R.version

_
platform       x86_64-unknown-linux-gnu
arch           x86_64
os             linux-gnu
system         x86_64, linux-gnu
status         Patched
major          2
minor          11.0
year           2010
month          05
day            19
svn rev        52043
language       R
version.string R version 2.11.0 Patched (2010-05-19 r52043)

Antonio Fabio Di Narzo, PhD.
Swiss Institute for Bioinformatics - Bioinformatics Core Facility
Office 2029, G?nopode, Quartier Sorge
CH-1015 Lausanne, Switzerland
Tel: +41 21 692 4087
Fax: +41 21 692 4065