Wikimedia Bugzilla is closed!

I have figured out a way to allow single line breaks made in the text editor to be interpreted as such.

With current functionality, you must include a <br> tag or make two line breaks to  have it appears as a single line break.

Changes made:

In WikiForumClass.php:

function parseIt( $text ) {
// included $wgWikiForumAllowSingleLine from LocalSettings.php
global $wgOut, $wgWikiForumAllowSingleLine;

// add smilies for reply text
$text = $this->prepareSmilies( $text ); 
//changes start here
if($wgWikiForumAllowSingleLine)
{
$text = nl2br($text); 
}
//changes stop here
$text = $wgOut->parse( $text );
$text = $this->parseLinks( $text );

Then from LocalSetttings.php if 

$wgWikiForumAllowSingleLine = true; // then single line breaks display as a single line
$wgWikiForumAllowSingleLine = false; // then single line breaks display as multiple lines.