The yellow stars are a sort of membership status, based on how many posts a person has.  The more stars, the more posts.

I don't know if there is a spell-check here, but when some people want to write a long post where they might make mistakes, they write it in a word processor, then copy and paste here.

Some current browser versions, like Firefox and Safari, will automatically spell-check as you type in the post in the box, by underlining in red for mis-spelled words.  Firefox is a free download.