fix

app/ui-message/client/message.js

@@ -483,7 +483,7 @@ Template.message.onCreated(function() {
 	const { msg, settings } = Template.currentData();
 
 	this.wasEdited = msg.editedAt && !MessageTypes.isSystemMessage(msg);
-	if (msg.tmid && !msg.threadMsg) {
+	if (settings.shouldCollapseReplies && msg.tmid && !msg.threadMsg) {
 		findParentMessage(msg.tmid);
 	}
 	return this.body = Tracker.nonreactive(() => renderBody(msg, settings));

app/ui-utils/client/lib/RoomHistoryManager.js

@@ -1,4 +1,3 @@
-import mem from 'mem';
 import s from 'underscore.string';
 import { Meteor } from 'meteor/meteor';
 import { Tracker } from 'meteor/tracker';
@@ -9,8 +8,8 @@ import { getConfig } from '../config';
 import { RoomManager } from './RoomManager';
 import { readMessage } from './readMessages';
 import { renderMessageBody } from './renderMessageBody';
+export const normalizeThreadMessage = (message) => {
 
-export const normalizeThreadMessage = mem((message) => {
 	if (message.msg) {
 		return renderMessageBody(message).replace(/<br\s?\\?>/g, ' ');
 	}
@@ -26,7 +25,7 @@ export const normalizeThreadMessage = mem((message) => {
 			return s.escapeHTML(attachment.title);
 		}
 	}
-}, { maxAge: 1000 });
+};
 
 export const upsertMessage = ({ msg: { _id, ...msg }, subscription }) => {
 	const userId = msg.u && msg.u._id;

app/ui-utils/client/lib/renderMessageBody.js

@@ -1,11 +1,32 @@
 import { callbacks } from '../../../callbacks';
 import s from 'underscore.string';
 
-export const renderMessageBody = (message) => {
+const generateKeyDefault = (...args) => args.map((item) => JSON.stringify(item)).join('-');
+
+const mem = (fn, tm = 500, generateKey = generateKeyDefault) => {
+	const cache = {};
+	const timeout = {};
+
+	const invalidateCache = (key) => delete cache[key];
+	return (...args) => {
+		const key = generateKey(...args);
+		if (!cache[key]) {
+			cache[key] = fn(...args);
+		}
+		if (timeout[key]) {
+			clearTimeout(timeout[key]);
+		}
+		timeout[key] = setTimeout(invalidateCache, tm, key);
+		return cache[key];
+	};
+};
+
+export const renderMessageBody = mem((message) => {
+
 	message.html = s.trim(message.msg) ? s.escapeHTML(message.msg) : '';
 
 	const { tokens, html } = callbacks.run('renderMessage', message);
 
 	return (Array.isArray(tokens) ? tokens.reverse() : [])
 		.reduce((html, { token, text }) => html.replace(token, () => text), html);
-};
+}, 5000, ({ _id, _updatedAt }) => (_id + _updatedAt));