This is a Snapshot how the Preview button looks along with the inline comments for Blogger, Pretty much good, something like preview scrap feature in Orkut.
The actual preview of comments also looks good, but for long comments you’ll have to scroll to see the full comments.
Things that can be tweaked : The preview comment is not fully matched with individual blog theme. As of now its a general preview. So if preview can be according to the Blog theme, would be a welcome move. Anyways good feature. Keep up the good work Blogger team.