As far as I can tell, evaluating the truth of notable claims involves quite a lot of discussion of philosophical points of contention, such as:
Questions of definition: Many claims being asked about have one or more ambiguous terms. Depending on the way that the answerer defines (or doesn't define) those terms, opposite conclusions can be reached as to whether the claim in the question is true. Sometimes it takes some discussion to discover and resolve this conflict of definitions, and this discussion is sometimes necessary to evaluate the logic of an answer (especially if the answerer doesn't explicitly define the ambiguous term).
Questions of provability and falsifiability: If an answer asserts that a claim that is not provable is proven true, or if an answer asserts that a claim which is not falsifiable is proven false, then there is naturally going to be some discussion on whether that is justified. This may occur because the answerer's implicit definitions of ambiguous terms changes the perception of the claim into something that is provable/falsifiable, or it may occur because of something more fundamental, like a disagreement on the definition of "falsifiable" itself, or it may occur because the answerer is simply in error. Discussion of these philosophical points helps to clarify the answerer's intent and allows for the proper evaluation of the answer's logic.
Questions of evidentiary standards: There are a myriad of different forms of evidence that are presented in answers here: scientific studies, new reports, document metadata, photographs, and many other types of evidence have been seen at one point or another. Discussions over whether individual pieces of evidence are admissible as proof, and whether the collection of evidence presented in an answer is sufficient to prove a statement, can shed light on the evidence itself and bolster or detract from the logic of the answer.
These are all purely philosophical points, and also serve a purpose: to clarify the intent of the answerer so that the answer's logic can be properly evaluated.
In the question Did President Obama tell President Trump he was close to starting a war with North Korea?, there was one such discussion under the accepted answer about part of the evidence provided, namely, the part of the New York Times report that said, "It is impossible to prove a negative, of course." The precise definition of "prove a negative" was gradually clarified, and it became clear why the answerer might have chosen to include this particular statement in the evidence they presented, with (as far as I can remember) no instances of verbal abuse or other misconduct, and all parties generally agreeing toward the end. My memory of this, unfortunately, is all I have at this point, since, rather than moving the discussion to chat, the discussion was deleted in its entirety, with only this message remaining:
Please avoid discussions on whether "it's impossible to prove a negative" is true or not -- they are perhaps worthy philosophical discussions but are worthless elsewhere and in particular here.
(As a side note, even after this comment was posted, both my reaction to it and the reaction of one of the other participants in the conversation were deleted, so that there is now no evidence of either the presence of a reaction or the upvotes that that reaction received.)
So that leads to the questions:
What is this site's policy regarding the "worth" of discussions that are arguably material to evaluating the logic of an answer? Based on the answer to that question, why was this discussion deleted, rather than being moved to chat?