What on earth is wrong with using it (and the recorder, e.g.) for folk, as well as (other) early music, HJ?
Did I miss something here?
You started an entire thread based on the premise that the so-called "English cittern" should be played more in English/British folk music. Your argument was not because the instrument sounded good, but because its name contains the word "English" and therefor you thought that its use was traditional in English folk music. At no point was your reasoning based on the musical properties of the instrument.
And now that more informed people have let you know what the *real* origins of the instrument are, you ask what's wrong with using it for folk. No-one ever said there was anything wrong with it. *YOU'RE* saying that there's something wrong with using non-English-origin instruments (which amounts to just about everything) in English folk music when those instruments happen to suit the music better than the alternatives. Unless you can keep your reasoning straight, why bother trying to start a debate?
FWIW, I play octave mandolin. There are a few songs that suit it perfectly - I could never sing Steve Knightley's "Galway Farmer" with any other instrument. There are also a lot of songs which don't suit it at all, but a guitar backing is perfect. I'd personally like to see more people playing octave mandolin, regular mandolin and viola in folk contexts, because I love the sounds they make. But realistically they're all minority instruments compared to violins and guitars, because they don't suit everything (or everyone).