LOL and just when we thought it couldn't get more confusing
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I just heard from a very early joiner of my forum that the unsubscribe wouldn't work for her. Turns out while most people in the database have "on" and "off" values - she has a "yes" value in her field! So at some point early on the values seem to have been yes and blank.
So now I'm tweaking the code to also watch for the "yes" value.