barretthunter:
One interesting issue is trying to work out whether spelling or grammar mistakes were deliberate! In a story, if someone for instance says, "The dog would'nt stay in it's basket", that's two mistakes. In fictional letters it could be a clever way of conveying information about the writer.
A very interesting point indeed, barretthunter. I suppose if the letter is from a schoolchild or servant (in Victorian or Edwardian times), for example, then one could assume some level of ignorance of grammar/punctuation/spelling. Otherwise, I think we need to look at the rest of the letter to decide. Is it supposedly from a lawyer or doctor or teacher? We would expect them to be well-educated.
Having said that, I have known maths teachers who couldn't spell or punctuate! And as for teachers of P.E. or Cookery - least said, soonest mended!
