It has to do with the advanced editor getting confused, and including part of the text you write in the wrong place in the HTML. I'll look into fixing it up (probably by making it impossible to get the text in the wrong place) for 2.0.0.

I've heard rumors around that Mozilla may support "contenteditable", which would make using the advanced editor possible under Mozilla on any Mozilla-supported operating systems. Of course, my hands are tied until Mozilla actually supports the feature.

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Jason Rhinelander
Gossamer Threads
jason@gossamer-threads.com