Perhaps off-topic, but .su is the TLD of the Soviet Union.
It's mostly completely distinct from the political question "what does it mean" regarding 2 letter top level domains, and the ISO3166 list, and the status of entities in the ICANN process. (well.. maybe not the last bit: ICANN has enough fights on its hands without trying to reclaim some namespace territory)
I agree that the use of ccTLDs by people who are not from a given country is OK - like having a .it or .me or a .tv domain as an American or a Brit etc. However the specific case of .io is, to put it politely, rather complicated.