Learn English – Reasons for using the same word for people and language of a country

I agree with @Bill's comment - to me, Anglophones are normally native speakers only.

But for me, that's largely because I wouldn't normally refer to "an Anglophone" in the first place. I use the plural form specifically to include people from many different countries who speak English as their mother tongue. Anglophones are representatives of whole linguistic communities.

But by most dictionary definitions, many non-native speakers here on ELU qualify as Anglophones (they speak English), so I can't deny that technically speaking Reg Dwight, for example, is an Anglophone. But in most contexts where I want to convey that someone speaks/understands English [fluently], that's how I phrase it. I've no real use for a word meaning person who speaks English fluently - either by birth, or through extensive exposure/familiarisation later in life.

For most people (read, me), Anglophone either identifies those specific members of a multi-lingual population having English as their primary language, or it collectively identifies all native speakers. But you can't normally "learn" your way into either category; you have to be born into it.

A plebiscite is a vote of the people. (Strictly it's a vote of "the common people" and could perhaps exclude people of a higher status [the word comes from Ancient Rome where it would exclude the Senate from the vote, and also not be binding on the Senate] but I don't think there's anywhere this is done today).

A referendum is a vote on an issue that has been referred to the people by the government (including if there is a mechanism by which the people can insist they do so).

Since a referendum involves the people voting, all referenda are plebiscites. Since about the only practical reason why there would be a vote of the people (plebiscite) is that an issue had been referred to them (referendum) in practice all plebiscites are referenda. In practice therefore they are the same.

As such, pretty much synonyms.

However, being terms about political procedure, they each have slightly different definitions in different jurisdictions and as such they are sometimes different in the contexts of a particular legal system.

In both Ireland and Australia referendum is used to refer to a vote to amend the constitution and plebiscite on any other matter. That difference is not the same in other jurisdictions.

It's often, but not always, the case that referenda are binding and plebiscites are not (though gauging the opinion of the people and then ignoring it puts any government into a fraught position). In the UK though their recent non-binding vote on leaving the EU was referred to as a "referendum". This might owe something to suspiciously-run plebiscites having been conducted in countries they were enemies of, or soon to become enemies of, at the time (France under Napoleon, Germany under Hitler), giving referendum a fairer connotation in that country than plebiscite.