Certainly it is, unless you're a solipsist. It's not proof (for any
number of reasons, mostly epistemological, phenomenological, and
psychological), but it is evidence.
Your definition of "evidence" seem to be incompatible.
Your use of "incompatible" has the wrong arity. It's a comparative
attribute.
Wikipedia says:
"Evidence in its broadest sense includes everything that is
used to determine or demonstrate the truth of an assertion.
[...]
Evidence is the currency by which one fulfills the burden
of proof."
Wikipedia is neither the arbiter of the English language nor an
authority on epistemological foundation. I don't know whether you did
a poor job of quoting whatever article that comes from, or whether the
article in question is poorly written; but that's not a useful
definition of "evidence" in relation to the interpretation of a
written statement.
Under any useful theory of the interpretation of writing - from the
most bluntly realist, intentionalist claims that an utterance means
what its author believes it means, to the most deferred, displaced,
non-transmissive ends of poststructuralism and neopragmatism - must
hold that the utterance is in some way *evidence* of an
interpretation, and the outcome of interpretation is meaning.
Even under Derrida's model of writing as the trace of an
eternally-deferred meaning; even under Lacan's locating the origin of
writing in the unconscious (and so original meaning is largely
inaccessible to the author); even under Foucault's rejection of the
author-function; even under Rorty's rejection of the model of language
as a channel for the transmission of an idea. Under all of these,
parole is still evidence of meaning.
Whether that meaning is the facade of a meaning that inheres in the
author's conscious thought is another question - that one's been
fought over endlessly since at least the beginning of the twentieth
century (and sporadically before that, probably since people first had
the leisure time to worry about inconsequentials). But if you accept
the axioms that 1) someone created the utterance and 2) that person
did so under the influence of meaning, then the utterance must be
*evidence* of that meaning. (It could be misleading, misinterpreted,
damaged, etc. But it's still evidence of that meaning.)
Oh, and by your own logic&terms, we have now strong "evidence",
that you *meant* to create the new word "forwhat"...
Evidence. Not "strong" evidence. Why? Because we can assign
probabilities to features of the surface form of the utterance. In
fact we have to; that's how we're able to process natural language at
all, with its ambiguities and errors.