Would be really helpful to preview posts before submitting, especially for longer replies with formatting. Right now I just have to hope it looks okay and edit if it doesn't.

Most phpBB forums have this. Would love to see it here.

Seconded. I've messed up formatting so many times. A preview button would save a lot of edits.

Also would be nice to have basic BBCode support — bold, italic, links, code blocks at minimum.