Anne thinks or utters to herself some sentence S. Who is the authority on what Anne's utterance means? Anne herself, I should think. That's not to say she's infallible here - just that if she's in error, then she must be in error by her own lights. We cannot foist semantic standards on her from without.
Example: Anne believes that 'whale' refers to a kind of really big fish. She may even be initially inclined to claim that "whales are fish" is true by definition. If so, we may doubt that she's thought sufficiently clearly about what she means by the word. But this is easy enough to check: simply bring to her attention the possible scenario we think she has neglected. We ask Anne to imagine that it turns out those big whale-shaped creatures in the ocean are warm-blooded, breathe oxygen, live-birth and nurse their young, etc., and are generally considered by scientists to belong under the category 'mammals' rather than 'fish'. Anne might make various responses:
(1) She may agree, on reflection, that if this scenario is actual then it turns out whales are mammals. So their fishiness is not built into the very meaning of her term after all. Our example served to bring out her implicit commitment to a broader concept than she had initially appreciated.
(2) She may insist that she means something different from the scientists et al. When she talks about 'whales', she means to talk about fish, and that's non-negotiable. If the world doesn't cooperate, that's the world's problem: maybe - she will say - the world doesn't contain any whales after all, but rather giant oceanic mammals that she mistook for whales.
It seems unlikely that she would choose the second option. We usually want to talk about what's in the world, so we use 'whale' to refer to whatever actually fills the whale-role, or "that kind of thing right there" (be it fish or mammal). But that's our choice, and there's no reason in principle why we couldn't stubbornly opt to use our words in the second kind of way. In such a case, it would seem a strange kind of 'linguistic paternalism' that would lead philosophers of language to insist that Anne - for all her reflection - remains just plain wrong about what her words "really" mean.
See also: Verification and Base Facts