Hi Ian,
thank you for your report.
This has nothing to do with the directory starting with an underscore.
What is happening here is that Org-mode uses the first line in the buffer,
"-----" in your case as the title of the document since no other title
is defined. Of course, the body-only export then discards the "title",
and you end up without your first line.
You could fix this with a dummy #+TITLE: line, or by putting anything at
all
in a earlier line, even above #+STARTUP, or by setting the :title option
in your publishing setup.
Another way would be
------------------------------------------------------------------------
#+STARTUP: showall indent
#+STARTUP: hidestars
#+OPTIONS: H:2 num:nil tags:nil toc:1 timestamps:t
#+TITLE: ADSL Connection Problems.
#+BEGIN_HTML
---
layout: post
title: {{{title}}}
tags: [gadgets, linux, test]
excerpt: Problems, problems!
---
#+END_HTML
Main text of post goes here.
------------------------------------------------------------------------
i.e using the {{{title}}} macro to insert the title into the right
place while having #+TITLE around to stop Org from grabbing
the first line.
One could also question if it makes sense to grab the title from
the buffer if body-only is set, and I have now changed it so
that in this case it will *not* take the title from buffer text.