This feature is inconsistent. The offline synther will accept a multi-word tag, putting it between quotes. The synth site splits up a multi-word tag in separate tags, even if the tag is put between quotes.
Perhaps this is only inconsistent between browsers? I just used Opera here on the site to add multi word tags in quotes to that panorama version of your photos.
I'll test other browsers this evening when I'm back to my other computer.
I am using IE9.
I've had good luck in the past with multi-word tags using various iterations of FireFox.