How have the courts interpreted “without prejudice” without prejudice communications?

In Pirie v. Wyld (1886), 11 O.R. 422, at pp. 427-428, Cameron, C.J., stated: “The authorities seem, though not very numerous, to be clear upon the first point, that letters written or communications made without prejudice, or offers made for the sake of buying peace, or to effect a compromise, are inadmissible in evidence. It seemingly being considered against public policy as having a tendency to promote litigation, and to prevent amicable settlements. “The language used in the cases is sufficiently wide to cover all communications made under the words ‘without prejudice’. The cases in which the rejection of such letters or communications has taken place have generally contained some offer of settlement.” and at p. 429, he continued as follows: “Mr. Justice Proudfoot in Corporation of York v. Toronto Gravel Road, &c, Co., 3 O.R. 585, at p. 593, thus presents his understanding of the rule: ‘The rule I understand to be that overtures of pacification, and any other offers or propositions between litigating parties, expressly or impliedly made without prejudice, are excluded on grounds of public policy’.”