Graeme,
It always used to be #if 0, you'll notice I've got another post about that in this same forum:) However, the latest core (which is based off SlickEdit 2010) does include this functionality, and it works quite well. Now you can put your preprocessors in and you don't have to use selective display, it will gray the text out, and although I haven't verified I believe it honors it in the tag files as well. Fantastic improvement to an otherwise fantastic tool, this is really just a nit. I'll send an email to the support team, and if I come to any resolution will respond here. Thanks for your help.