Hello Daniel,
the problem is in the client libraries using FreeType to render the
text. 2.2.1 provides both outline and bitmap emboldening functions,
and the latter is capable of generating output exactly equal to your
"good" screenshot.
more precisely, the problem is that these libraries only use the
vector emboldening algorithm, which only gives satisfying results
with anti-aliase text.
I would provide a patch if I had time, I recommend you to file
bugs against libXft, Cairo, and probably OpenOffice.org if this
is a big concern to you.