Lately I saw several posts that were either badly formatted (did not use <p> tags for paragraphs just white spaces). It seems the preview feature is not really convincing. What else can I do to encourage people to format their posts better?

Duplicate posts: I also saw people posting the same message several times one after the other.
I guess the server did not give them a quick response so they realoaded the browser. In effect they created two post.
I am working now on a feature to hide a post but I would like to get ideas on how to solve this issue too.

And I just had a simple idea which could improve the bad formatting.

It would be reasonable to convert a double-linefeed combination into "<br /><br />". This would save me a lot of typing and make much of the unformatted text more readable. The only trouble would be that you might not want to do this if there is already a "<br>" or "<p>" between the paragraphs. If necessary you could add a checkbox to "Preserve blank lines", allowing people to turn this feature off if necessary.

Just a thought, but this would make it much more convenient for me when posting since typing all the format codes is cumbersome to say the least.