Markdown editor
Edit visually: headings look like headings, bold is bold. One sunken surface; the toolbar is a strip on it, no lines between the parts.
One row, no File button
rows = 1 makes the surface one line high (it grows with the text), files = "off" takes the File button away: pasted or dropped files are left to the page (the comments block uses this inside its attach form).
Read only
readonly = "true": the Markdown shown formatted and nothing else — no toolbar, no field. The comments block draws its texts so.