Indent the first line in each paragraph in Preview Mode

You can do a workaround, but it’s not as straight forward as just typing markdown in the Editor pane.
e.g. You could add

article {
    padding: 1em;
}

.first {
    text-indent: 2em;
}

to your css file, then at the start of your paragraph, paste
<p class="first">
in the Editor, but that really defeats the purpose of the simplicity of markdown. Maybe the dev’s can implement a solution when the WYSIWYG editor is released.