for v6, this is easy to do, you just need to add
code:
$instant_ubbcode = $html -> instant_ubbcode();
to the sendprivate.php somewhere, and insert
code:
$instant_ubbcode
into the template for it, and also will need to change the textarea tag in the template to add the attributes:
code:
onkeyup="storeCaret(this);" onclick="storeCaret(this);"
if you're adding it to v5, you'd need to copy over the instant_ubbcode function into the html class, change the textarea and more or less make the same changes. That, and you'd need some of the new smiley images.