Taciturn conduct, which requires that you not use your voice at all. This mostly means that you can’t #chat with things; there probably aren’t currently enough things in the game which require or incentivize speech to make such a conduct meaningful. To that end, a useful #chat system that lets you do many things with many types of monsters (e.g. the one described in #2576) would be useful.

Certain messages like “You scream in agony as your body begins to warp” would need to be changed to special YAFMs if you have taciturn conduct intact.