There's no pronoun for that sentence, so it's left undefined who it's talking about. It doesn't mean the poster. It also doesn't really matter, if one former Singaporean politician dropped their "first name" then it's being used as an example that others may too.
It means that LKY himself stopped using the name Harry, for whatever reason. His (LKY) Wikipedia article states when, but not why - it cites his autobiography so that may be a useful source if you are interested to learn more.
Also it was his grandfather that gave him the name “Harry”, not his parents.