Chofetz Chaim Daily 27 Av 1:10 Asur, even without details, to hint towards an old fight. 1:11 Asur to write rechilus. Asur to tell a store owner that ploni badmouthed his merchandise.
Chofetz Chaim Daily 28 Av 2:1 Asur to say rechilus to an individual, and worse in public. 2:2 AVAK rechilus is also asur. When talking about ploni to either an overly sensitive person or someone who doesn’t like him, one must not say anything that they’ll misunderstand as an offensive comment.