src/m2d/event-dispatcher.js

@@ -276,8 +276,22 @@ async function bridgeThread(event) {
 		return true;
 	}
 	catch (e){
-		if (e.message?.includes("50024")) return false; //Tried to created a thread in a thread? Too bad! Discord users will just see normal replies, and Matrix uses won't get a thread-room. Same case as for message-not-bridged, except there at least exists a HYPOTHETICAL solution (just one so unwieldly that it's nonsensical to dedicate resources to), wheres here I don't know what could possibly be done at all.
-		else throw e; //In here (unlike in matrix-command-handler.js), there are much fewer things that could "intentionally" go wrong (both thread double-creation and too-long names shouldn't be possible due to earlier checks). As such, if anything breaks, it should be reported to OOYE for further investigation, which the user should do when encountering an "ugly error" (if they follow the „every error should be reported” directive), so this is re-thrown as-is (no stacktrace-breaking exception wrapping) to be turned into such an "ugly error" upstream.
+		if (e.message?.includes("50024")){
+			api.sendEvent(event.room_id, "m.room.message", {
+				body: "Hey, please don't do that! This room is already a thread on Discord - trying to embed threads inside it will not work. The user will just see a regular reply.",
+				"m.mentions": { "user_ids": [event.sender]},
+				"m.relates_to": {
+					event_id: eventID,
+					is_falling_back: false,
+					"m.in_reply_to": { event_id: event.event_id },
+					rel_type: "m.thread"
+				},
+				msgtype: "m.text"
+			})
+			
+			return false;
+		}
+		else throw e
 	}
 }