You have to be a full member of this site for your posts to show.That means you have to have someone approve your account before you are a full member.
Give it some time and your account should be activated
Why was my comment removed?
One word. Rules
Most of the time your post has been removed to enforce the rules of the site.Meaning your post was in some way breaking/bending the rules and you got caught.Unless you got a warning from site Admin/Moderators you don't have to worry about it.