[razorback-bert]

exemplified by a story that an acquaintance told me. . . my informant

My acquaintance becomes my informant strikes me as odd.

[A. Goodwin]

It's a bit of an old-fashioned useage, but it really doesn't have the law enforcement intelligence-gathering connotation that has become common; here, it just means the person who is imparting news, telling the story.