[ESS] LocalWords, flyspell and noweb mode

[Kasper Daniel Hansen]

I am used to, in tex mode, to be able to have buffer local words for
flyspell / ispell.  In tex-mode (AUCTeX) I do this with lines like

% LocalWords: splicing, CpG, methylation

This essentially acts as an additional dictionary for ispell (and
hence flyspell-mode which I am using).  My impression is that this
ought to work in any buffer where I am using flyspell, and that I just
need to precede the LocalWords statement by a comment character (which
in tex is %)

Now, I want to do the same for Rnw files, and it seems to fail (fail
as in not making a difference wrt fontification).  My guess is that
this may have something to do with how we really run several major
modes inside a Rnw buffer through noweb.  I have checked that % is the
right comment char by using comment-dwim to comment out a line at the
end of the Rnw file.

How do people deal with this?  I am currently using (GNU) Emacs 23.3.1
on OS X (self-compiled), and I also see it under 23.3.1 on Linux
(self-compiled), 24 svn on Linux and OS X (self-compiled) .  I think
this is a general Emacs issue and not special to my setup.

Kasper