As it turns out, the link in the question hinted at a working solution in the form of xclip:
pandoc -S file.mkd | xclip -t text/html
...and then I can paste it straight into the document in libreoffice, properly formatted. This works with the versions of the programs in the Ubuntu 13.04 repositories (pandoc 1.10.1 and xclip 0.12) -- the -t option for xclip especially is only in version 0.12 or above. The -S option of pandoc makes it produce 'typographically correct output', so -- is turned into an en-dash, --- is turned into an em-dash, and a few other things.
If you want to use the ctrl-v clipboard, use:
pandoc -S file.mkd | xclip -t text/html -selection clipboard
Edit: if you're running OS X (with pbcopy rather than xclip), use:
pandoc -S file.mkd | textutil -stdin -format html -convert rtf -stdout | pbcopy
To transform selected text without creating a file, you can use:
xclip -o | pandoc -S | xclip -t text/html
...this can, of course, be mapped to a keyboard shortcut.
This can work well with a number of text markup formats as input, see the pandoc guide for some more information on how to accomplish this (you might need to use the -f/--from/-r/--read option, especially if you're using the xclip|pandoc|xclip version).
As a side note, you can also read an already-existing HTML file into xclip:
xclip -t text/html <file.html
or
<file.html xclip -t text/html
Best Answer
This sort of syntax is typical for a wiki engine, but they mostly propose similar syntaxes other than Markdown. However, you can try MDwiki:
It really is that simple. Follow the tutorial. This is a renderer, not an in-page editor.