allow escaping the first slash to not write a command

src/components/views/rooms/SendMessageComposer.js

@@ -18,7 +18,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import dis from '../../../dispatcher';
 import EditorModel from '../../../editor/model';
-import {htmlSerializeIfNeeded, textSerialize, containsEmote, stripEmoteCommand} from '../../../editor/serialize';
+import {htmlSerializeIfNeeded, textSerialize, containsEmote, stripEmoteCommand, unescapeMessage} from '../../../editor/serialize';
 import {CommandPartCreator} from '../../../editor/parts';
 import {MatrixClient} from 'matrix-js-sdk';
 import BasicMessageComposer from "./BasicMessageComposer";
@@ -54,6 +54,7 @@ function createMessageContent(model, permalinkCreator) {
     if (isEmote) {
         model = stripEmoteCommand(model);
     }
+    model = unescapeMessage(model);
     const repliedToEvent = RoomViewStore.getQuotingEvent();
 
     const body = textSerialize(model);

src/editor/serialize.js

@@ -74,3 +74,16 @@ export function stripEmoteCommand(model) {
     model.removeText({index: 0, offset: 0}, 4);
     return model;
 }
+
+export function unescapeMessage(model) {
+    const {parts} = model;
+    if (parts.length) {
+        const firstPart = parts[0];
+        // only unescape \/ to / at start of editor
+        if (firstPart.type === "plain" && firstPart.text.startsWith("\\/")) {
+            model = model.clone();
+            model.removeText({index: 0, offset: 0}, 1);
+        }
+    }
+    return model;
+}