That's interesting and I didn't know that it was a common occurrence, although, still, in the example you showed wouldn't that be because it's being used in a f

That's interesting and I didn't know that it was a common occurrence, although, still, in the example you showed wouldn't that be because it's being used in a face to face situation (or in writing if you're narrating human discourse, like in a novel, or something along those lines), the 'and by the way' has the effect of highlighting what comes after (and I would guess it isn't unique to British English but a common occurrence in many more languages/cultures). Anyway, I just found it ironic in the context and I still see it as, consciously or not, that idea is projected by the choice of their words, specially given it's in written form, if this were two blokes talking to each other it would be different - and there's nothing wrong with it either way, plus, I can be wrong, which is fine too - the same way I don't want thought police for me I don't want it for anyone else either.