Threaded Conversations
*This is only applicable to channels within Teams, not Chats between one or more people*
When someone starts a conversation in a channel, you can just "Reply" to that message instead of starting a new conversation at the bottom. This keeps the channel nice and neat, as everything about one topic can stay in one thread. Any new topic can be a different conversation.
It is really easy to do - just click "Reply" under that conversation.
Example with threaded conversations: