1. The republication rule: Say that Alan writes, “Betty alleges Charlie committed armed robbery.” Alan’s statement is literally true: Betty did make the allegation. But the statement Alan is reporting on (Betty’s statement) is false. American libel law has long adopted the “republication rule,” under which Alan is potentially liable for defamation — if Betty’s allegation actually proves to be false — even if he expressly attributes the statement to Betty. (See Restatement (Second) of Torts § 578.)
And this is true even if Alan distances himself from the allegation, for instance by saying that Charlie has denied the statement, or that Betty has reason to lie. The principle is that “Tale bearers are as bad as the tale makers.”
"The original post is really quite careful in its epistemic status and in clearly referencing to sources claiming something."
This is insufficient. See: https://www.washingtonpost.com/news/volokh-conspiracy/wp/2017/01/13/when-there-is-serious-reason-to-doubt-rumors-and-allegations-is-it-libelous-to-publish-them/