Even if there is a specific "set of words"< NyanCat >
they aren't going to disclose them.
If your forum posts are being removed, it is because craigslist staff don't want them on their site.
If your *ads* are being removed, the only real way to figure out what you're doing wrong is to follow the instructions staff provide about going to the flag help forum, and following the directions there about what information to provide.