Last modified: 2014-02-12 23:35:42 UTC
If you include a full size image, like: [[File:Lead electrolytic and 1cm3 cube.jpg]] it downloads the whole thing, then hotlinks Wikimedia Commons anyway.
I tested this at <http://piramido.wmflabs.org/wiki/Bug_44295>. "[[File:Lead electrolytic and 1cm3 cube.jpg]]" as input produces the following HTML output: --- <a href="/wiki/File:Lead_electrolytic_and_1cm3_cube.jpg" class="image"><img alt="Lead electrolytic and 1cm3 cube.jpg" src="http://upload.wikimedia.org/wikipedia/commons/e/e6/Lead_electrolytic_and_1cm3_cube.jpg" width="5260" height="3341" /></a> --- "[[File:Lead electrolytic and 1cm3 cube.jpg|10px]]" as input produces the following HTML output: --- <a href="/wiki/File:Lead_electrolytic_and_1cm3_cube.jpg" class="image"><img alt="Lead electrolytic and 1cm3 cube.jpg" src="/srv/mediawiki/images/thumb/e/e6/Lead_electrolytic_and_1cm3_cube.jpg/10px-Lead_electrolytic_and_1cm3_cube.jpg" width="10" height="6" srcset="/srv/mediawiki/images/thumb/e/e6/Lead_electrolytic_and_1cm3_cube.jpg/15px-Lead_electrolytic_and_1cm3_cube.jpg 1.5x, /srv/mediawiki/images/thumb/e/e6/Lead_electrolytic_and_1cm3_cube.jpg/20px-Lead_electrolytic_and_1cm3_cube.jpg 2x" /></a> ---