Always use OOYE bot to send thread start context

d2m/converters/message-to-event.js

@@ -108,7 +108,8 @@ async function messageToEvent(message, guild, options = {}, di) {
 		const event = await di.api.getEvent(roomID, eventID)
 		return [{
 			...event.content,
-			$type: event.type
+			$type: event.type,
+			$sender: null
 		}]
 	}
 

d2m/converters/message-to-event.test.js

@@ -485,6 +485,7 @@ test("message2event: thread start message reference", async t => {
 	})
 	t.deepEqual(events, [{
 		$type: "m.room.message",
+		$sender: null,
 		msgtype: "m.text",
 		body: "layer 4",
 		"m.mentions": {}