Hi Saguaros!
I solved this. The problem was in template override:
../templates/t4_blank/html/com_content/article/default.php. In this file, i used $this->item->fulltext to display the content. I compared with the original T4 framework file that render the Joomla article page, it uses $this->item->text in ../plugins/system/t4/themes/base/html/com_content/article/default.php
I changed it to use ->text instead of ->fulltext, Komento does get displayed!
Maybe this will help somebody.