hehe ... continuing the discussion with myself. I found that nextpage is evaluated in query.php starting around line 1511.
Before the line if ( preg_match('/<!--nextpage-->/', $content) ) {
I added this:
$pos1 = stripos($content, '<!--nextpage-->');
if ($pos1 === false) { /* we did not find a nextpage tag so add automatically */
$content = str_replace("< /P >", "< /p >", $content);
$save = explode('< /p >', $content);
$content = '';
$count = 1;
foreach ($save as $a){
$content .= $a.'< /p >';
if ($count % 10 == 0){
$content .= '<!--nextpage-->';
}
$count = $count + 1;
}
}
The hack first checks if the content contains nextpage tags already. If yes, then nothing is done. If no nextpage tags are found, the hack will insert nextpage after each 10th closing paragraph tag. Wish I could make this a plugin but I don't think there's anywhere to hook to have the right impact.