Hi Burak,
most API commands can also be configured in the /etc/bigbluebutton/bbb-html5.yml file (this is an override for /usr/share/meteor/bundle/programs/server/assets/app/config/settings.yml).
If you add public.userReaction.enabled: false and restart BBB, you should see the reaction bar dissappear.
Do be careful to use yml-notation.
Regards,
J.