The content may be sourced for some countries, but not for all: therefore it is inappropriate for the infobox and for the lead to present it as if it is specifically aimed at communism generally. What is common to the day in all countries that mark the day is totalitarianism and Stalinism, ergo I tweaked the lead to reflect commonality. As noted to you, you're welcome to add 'communism' to nation-states who have included 'communism' where it is sourced. You are not welcome to misrepresent the principle common features between the nation-states that have designated it as a day of remembrance. This is an encyclopaedic source, not a POV-pushing source.