I think this is because JQuery treats your second case as a CSS selector rather than an HTML fragment. Since you probably don't have any elements matching "᫼" in your document, you are basically appending an empty set of elements to your body.
try using directly
$("body").append('█');
This prevents JQuery from having to guess if your string is and HTML fragment or a CSS selector. When passed a String, the append method assumes it is an HTML fragment.