Hi I have a small comment shoutbox type cgi process running on a server and currently when someone leaves a comment I simply format that comment into html i.e
<p class="title">$title</p>
<p class="comment">$comment</p>
and store in a flat file.
Would it be faster and acceptably low in LOC to reimplement the storage in xml or json, in a simple spec of my own or stick with the simple html route?.  
I don't want to use relational database for this.
If a flat file is fast enough, then go with that, since it's very simple and accessible. Storing as XML and JSON but still using a flat file probably is very comparable in performance.
You might want to consider (ignore this if you just left it out of your question) sanitizing/filtering the text, so that users can't break your HTML by e.g. entering "</p>" in the comment text.
fastest way to store comment data python