The new preview is a step in the right direction and I appreciate the feature but it’s not what I hoped.
The preview doesn’t render all the blog formatting and styling such as syntax highlighting of code blocks, clickable hashtags, MathJax, and YouTube videos and other embedded media. My blog has custom CSS for scrolling code blocks that are wider than the margins but the preview ignores it and wraps long lines instead.
The preview shows the post in an overlay that prevents from editing the Markdown source. I prefer having a preview in a separate page so that I can compare the source and preview side by side as well as edit while I check the preview.
A full preview would go through all the steps for formatting, styling, and publishing all the elements of a post but publish to a temporary private page instead of to the public blog. The preview I need should render an exact, complete copy of the post that’s going to be published to the blog.