A possibly rather innocuous comment was made a few days ago at Unionist Lite but I've seen this incorrect claim used on Slugger O'Toole to bait unionist commenters on a number of occasions: something along the lines of "Sure you're all subjects up there, I'm much happier being a citizen... blah, blah."

Well, actually, no we're not. There did exist a class of person known as a British Subject and, while technically it still exists, for all intents and purposes it was abolished long ago.

Follow up:

A little more detail

Up until 1946, anyone born in a Commonwealth country (except the Free State) was a British Subject and this was their sole nationality status. Then in 1946 Canada enacted its own citizenship laws which led to a review in 1948 where the commonwealth collectively decided that each country would have its own citizenship but citizens would also share the common status of British subjects (AKA Commonwealth Citizens).

The idea was that practically all British subjects would acquire one or more of the new citizenships being created, with those who didn't becoming a "Citizen of the United Kingdom and Colonies".

However India and Pakistan didn't award citizenship to everyone who was born in those countries, so Britain refused to include those countries in the section of the Act that enacted the above, meaning that subjects from India or Pakistan who didn't qualify for citizenship of India or Pakistan remained British subjects without citizenship. Also, because the Free State was about to leave the Commonwealth, special provision was made to allow British Subjects from there to continue to hold British Subject status if they so wished (This applies only to those born before 1949).

Since 1983, the term British Subject doesn't apply to Commonwealth Citizens, which is now their official title. The only class of people who remain British Subjects are those British Subjects without citizenship mentioned above. British Citizens are not subjects. In fact, only those who are British Subjects by virtue of being born in the Free State before 1949 who apply for British Citizenship can be both subjects and citizens - anyone else loses their British Subject status when they apply for any citizenship. They also cannot transmit the status of British Subject to their children.

All information taken from Wikipedia entries:
British nationality
British subject
History of British nationality law