The FAQ will never be complete, and we always expect that there will be people out there who know better than we do about something or other. We always need to be put right about whatever we've got wrong, and suggestions for improvements, particularly covering areas we've missed, are always needed: mail anything you have to the maintainers.
If you have actual material to submit, your contribution is more than ever welcome. Submission in plain text is entirely acceptable, but if you're really willing, you may feel free to mark up your submission in the form needed for the FAQ itself. The markup is a strongly-constrained version of LaTeX - the constraints come from the need to translate the marked-up text to HTML on the fly (and hence pretty efficiently). There is a file markup-syntax in the FAQ distribution that describes the structure of the markup, but there's no real substitute for reading at least some of the source (faqbody.tex) of the FAQ itself. If you understand perl, you may also care to look at the translation code in texfaq2file and sanitize.pl in the distribution: this isn't the code actually used on the Web site, but it's a close relation and is kept up to date for development purposes.