Sounds good :) For those, who want to do it theirselves:

1. Open inbox.php

2. Change the code there to look like this:

Near line 400:

[code]if (!$isforward) {
			echo "<div class='uddeim-messageheader'>".$headerstring."</div>";
			echo '<A href="#showform">»Go to textarea</A><p></p>';
			echo "<div class='uddeim-messagebody'>".uddeIMreplyquoteMarkup($bodystring,$config->quotedivider)."</div>";
		}[/code]

Near line 460:

[code]if (($isforward && $config->allowforwards) || !$disablereply) {	// it is a forward or you can reply to the message
		// show reply form
		echo '<A name=showform></A>';
		if(!$trashmessage) { // but only if not already moved to trash[/code]

Now there is a link above each message that leads directly down to the textarea :)