It may be late, but I'm having the same problem. I'll reply to you and the people who arrived in the search.
Rewrite this.
moodle/mod/chat/gui_ajax/module.js [About Line 248]
//li.all('td').item(1).append(Y.Node.create('<div></div>').append(talk).append(' ').append(beep));
li.all('td').item(1).append(Y.Node.create('<div></div>').append(talk).append(' '));