This might come off as pedantic, but LyX is explicitly designed to be What You See Is What You Mean (WYSIWYM) rather than What You See Is What You Get (WYSIWYG). It gives you the gist of how things will end up without attempting to actually represent the final LaTeX output while you edit. It's an incredible piece of software, and I strongly prefer it over raw LaTeX despite the fact that I learned LaTeX first.