it is easy to display markdown text rendered as html in a view

{{=gluon.contrib.markdown.WIKI(row.body)}}

But currently there is no What You See Is What You Get Editor for Markdown. To get around this you can use a WYSIWYG Editor form HTML and convert the HTML to Markdown. However the problem with most WYSIWYG Editors is that they replace the texarea that you want to edit in a way that you cannot submit the textarea via Ajax (plug-in/LOAD with ajax=True)

To solve the second problem I chose http://code.google.com/p/jwysiwyg/ as an editor and created my view:

<script type="text/javascript" src="{{=URL(request.application,'static/jwysiwyg','jquery.wysiwyg.js')}}"></script>
<link rel="stylesheet" media="screen,projection" type="text/css" href="{{=URL(request.application,'static/jwysiwyg','jquery.wysiwyg.css')}}" />
<script type="text/javascript"> $('#no_table_body').wysiwyg(); </script>
<h1>Comments</h1>
{{import gluon.contrib.markdown}}
{{for row in rows:}}
    <h2>{{=row.title}}</h2>
    {{=gluon.contrib.markdown.WIKI(row.body)}}
{{pass}}
<h1>Post a comment</h1>
{{=form}}

To convert the HTML to Markdown I used http://www.aaronsw.com/2002/html2text/ and created my controller:

import applications.movie.modules.html2text as html2text
from gluon.sqlhtml import form_factory
form=form_factory( Field('title',requires = IS_NOT_EMPTY()), Field('body','text',requires = IS_NOT_EMPTY()) )
if form.accepts(request.vars, session):
    form.vars.body = html2text.html2text(form.vars.body)
    db.comment.insert(title= form.vars.title, body = form.vars.body)
rows = db(db.comment.id>0).select()
return dict(form=form,rows=rows)