Hmm, I'll check to see if they are getting marked as spam. I'm sorry, @ALLY78!
Also - if you edit posts more than 5 times, I think it will remove the post as spam, but I don't think you typically do this.
I don't think there is a word limit. Are you always logged in when it does this? The forums do auto-log people out pretty quickly.
edit - looks like 3 posts had been marked as spam. I went ahead and marked them as not spam!