As psyblast said it can be added to newthread and q-reply in the same way as newreply. I did add a <br> and retain the:
PHP Code:
<a href="javascript:checklength(document.vbform);">[check message length]</a>
that way anyone who's browser doesn't utilize the count, progress bar or whatever can still check message length somehow. I may also add a note about it not working in all browsers. How to do it in a clean way is what I am trying to figure out now. Nice addition though!