[VBDev]

As I have no mean to test, could you try that:

Delete the last modifications so that now you just have

PHP Code:

AND $forum['showsign'] 


instead of

PHP Code:

AND ($forum['showsign'] OR THIS_SCRIPT=="private") 


And before

PHP Code:

        // get signature
        if ($post['showsignature'] AND ... 


Add

PHP Code:

if(THIS_SCRIPT=="private")
    $forum['showsign']=1; 


But I still find it strange so I hope this will fix