Ok, i checked throgh the function_bbcodeparse.php again, and i think i found out what was wrong
i classify it as Gamma now, as it works with wysiwyg as well now.
Just the nested tags don't work 100% perfect
btw. as wysiwyg uses JS, it's not true wysiwyg with this hack, as things are parsed in the editor won't be parsed on showthread.
Maybe i'll write a more wysiwyg version when i find the time, but it's working, at that's most important