When you are buying a pickled ham in a barrel -- that's what a "pig in a poke" means, iirc -- you are obviously there at that time to buy that kind of thing. You are paying attention to the verbal offer of the seller and he is paying equal attention to you -- the contextual framing, the desire of both parties in that transaction at the time to be completely understood is obvious. That's why the buyer's tesimony that the seller verbally offered a "pig on a poke" rises above hearsay to the status of a "verbal act".
The informal and off-hand context of Terri's claimed remarks have none of that framing. They remain hearsay and should have been ignored by the court for what they are -- mere hearsay.
That's all without examining Micheal's motives or veracity.
Yet -- I said "both" or your final paragraph's cases apply. There is obvious reason to question Micheal's motive, and reasonable suspicion as to his veracity.
I've seen some people take a hard position that testimony from witnesses regarding what Terri (or anyone else in Terri's position) once said is not evidence of her wishes. People taking this position seem to believe that the only acceptable evidence regarding the person's wishes should come directly from the hand or mouth of the incompetent person herself.
That's simply not correct. Evidence in the form of testimony regarding an incompetent person's oral statements is admissible to prove whether the person would choose to continue receiving life-prolonging treatment.
That's not to say such testimony must necessarily be believed: it's up to the trier of fact to determine the credibility of the testifying witness and how much weight that witness's testimony should receive.
Now, back to the question. In the 1994 case In re Davey, the Florida Supreme Court approved the following definition of the clear and convincing evidence standard:
There must be more than a "preponderance of the evidence," but the proof need not be "beyond and to the exclusion of a reasonable doubt." This intermediate level of proof entails both a qualitative and quantitative standard. The evidence must be credible; the memories of the witnesses must be clear and without confusion; and the sum total of the evidence must be of sufficient weight to convince the trier of fact without hesitancy.
Clear and convincing evidence requires that the evidence must be found to be credible; the facts to which the witnesses testify must be distinctly remembered; the testimony must be precise and explicit and the witnesses must be lacking in confusion as to the facts in issue. The evidence must be of such weight that it produces in the mind of the trier of fact a firm belief or conviction, without hesitancy, as to the truth of the allegations sought to be established.
How incredible, then, that Greer was not overturned for relying upon inadmissible evidence. Amazing that the appeals court would explicitly affirm his finding that clear and convincing evidence existed.