This seems to be the "bug" that has been added to the FQXi script (I've removed bits so it can be seen). It's up to FQXi to clean up their act:
a href="https://www.addthis.com/bookmark.php?v=250" onmouseover="return addthis_open(this, '', 'http://fqxi.org/community/forum/topic/3244#post_148428', 'In a comment on 'Constructing a Theory of Life', Lorraine Ford writes 'Re " constructing="" a="" theory="" of="" life": br="">Physicists seem obsessed...'')" onmouseout="addthis_close()" onclick="return addthis_sendto()"> img src="https://s7.addthis.com/static/btn/lg-share-en.gif" alt="Bookmark and Share" style="border:0" width="125" height="16"> a>"
script type="text/javascript" src="https://s7.addthis.com/js/250/addthis_widget.js?pub=xa-4a2d86f24c5ca30a"> /script