Comment by gjm11

There is no question whatever: the sentence contains misspelled words. "They're" is misspelled as "Their", "to" as "too", "see" as "sea", etc.

There is also no non-words. It happens that today's spelling checkers are generally just non-word detectors. This doesn't mean that anyone defines "misspelled" to mean "misspelled in such a way that the result is not a word at all".

And yes, a non-word detector is still very useful, and it's much much easier to make than something that also determines reliably when words are misspelled in ways that produce other words, so there's lots of software out there (perhaps essentially all of it) that contains only a non-word detector.

I think it's perfectly reasonable to define "spelling checker" to include mere non-word detectors. Or for that matter non-common-word detectors. (I expect most spelling checkers will reject "hight", and very sensibly because if someone types that they probably meant "high" or "height" or something -- but it's a perfectly good word, albeit a rare and archaic one.) But there's no way it's correct to say that "sea" isn't misspelled in that sentence merely because the mistake happens to have produced something that's an English word.