Rocket.Chat/app/ui-message/client/messageThread.html

<template name="messageThread">
	<q role="button" aria-label="{{_ " Open_thread "}}" class="thread-quote">
			<div class="thread-quote__message js-open-thread">{{> icon icon="thread" block="thread-icons"}} <span class="message-body--unstyled">{{{parentMessage}}}</span></div>

		{{# if following }}
		<div role="button" class="rc-tooltip js-unfollow-thread" aria-label="{{_ "Following"}}">
			{{> icon icon="bell" block="thread-icons"}}
		</div>
		{{else}}
		<div role="button" class="rc-tooltip js-follow-thread" aria-label="{{_ "Not_following"}}">
			{{> icon icon="bell-off" block="thread-icons"}}
		</div>
		{{/if}}
	</q>

	<div class="thread-replied js-open-thread">
		<button aria-label="{{msg.u.username}}" class="thumb user-card-message" data-username="{{msg.u.username}}">
			{{> avatar username=avatar}}
		</button>
		<span role="button" class="js-toggle-thread-reply thread-reply-preview color-primary-font-color">
			{{# if threadMessage}}
				<span class="message-body--unstyled">{{{threadMessage}}}</span>
			{{else}}
				<div class="{{class}}" dir="auto">{{{body}}}</div>
			{{/if}}
		</span>
	</div>
</template>