Fix for ticket #2910: fix inconsistencies in notice posting response display that...

Fix for ticket #2910: fix inconsistencies in notice posting response display that broke help command, could be generally wonky

Previous code was importing nodes from the XHR result into current document, then pulling text content of what might be the right element, then concat'ing that straight into HTML. Eww! Now pulling the text content straight from the XHR result -- same element that we check for existence of -- and using jQuery's own text() to do the getting and setting of text. Also note that some browsers might have been pulling HTML instead of text, or other funkiness.