Try in your draft [[Special:Search/New York filesize:<100]], the link is not created. [[Special:Search/New York filesize:100]] is.
This is unfortunately due to the incredibly weird way that MediaWiki deals with page titles. < is not valid as part of a page title, so it messes it up, even though Special:Search isn't a page in the way the user thinks about it. I really don't know what we can do about this without totally reworking MediaWiki core.