I use Telerik RadEditor in my CMS. It is VERY robust and has several connection points that allow you to expand the functionality to meet your needs. It does not have (afaik) a real-time view similar to that used by one StackOverflow, but it could possibly have been added if you wanted to.
However, it does provide a photo upload / post function that you mention, besides the fact that you can upload documents and some other media. The downside is that the controls are pretty expensive, around $ 1,000, I think. Fortunately, my company covers the costs :)
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