var array = document.getElementsByTagName('blockquote');
for(var i = 0; i < array.length; i++) {
   array[i].savedContent = array[i].innerHTML;
   array[i].innerHTML = '';
   array[i].style.margin = 0;
}

how about something like this

<br class="b"><blockquote>
commentary
</blockquote><br class="b">

then toggle the display of class b. so
if blockquote is display:block class b is display:none

and
if blockquote is display:none class b is display:inline