ok, I thought you wanted to export the entire database in xml format.
If you want to export just "posts", you can do it with phpadmin too : you could export only some tables, e.g. : the qa_posts table, and the tables that have a relationship with it.
About the "reader-friendly" format, sorry but I've not understood ....
Which file extension are you thinking about ? What do you mean for "reader-friendly" ?