I like the idea of a default entry, and would suggest the ability to disable it in user settings. I also like the idea that "preview" persists until some specific formatting action is taken. Perhaps this behavior can go away after a suitable level has been attained? As to what level, I now wonder if there incorrigibles who persist with major, obvious, formatting problems beyond, say level 5...or even 4.
Like moklevat I too like the idea of a default entry, that could be disabled through user settings.
Perhaps even in the form of a template. With predefined sections for the title, question and built in tags for code.