Rocket.Chat/apps/meteor/app/threads/client/threads.css

.thread-empty {
	padding: calc(2 * var(--default-padding));
}

.thread-list {
	overflow-x: hidden;
	overflow-y: auto;

	word-wrap: break-word;
	flex-grow: 1;
	flex-shrink: 1;
}

.contextual-bar__content.thread,
.contextual-bar__content.discussions,
.contextual-bar__content.channel-settings,
.contextual-bar__content.keyboard-shortcut-list,
.contextual-bar__content.threads {
	padding: 0;
}