Pay attention to which box you’re typing in! To reply to a message, click the Reply button directly underneath the message you're responding to. This ensures that your response gets included in the conversation thread and that the other people participating in the thread will be notified. Conversations are sorted chronologically, so if you were to reply to a conversation by starting a New Conversation, the reply gets separated from the rest of the conversation.
Which is which? When posting to a Channel in Teams, you have two options:
Reply
Click Reply right underneath the message when you are responding to an existing thread of conversation. For example, if someone asks a question, it's always best to respond using a reply so the person knows you are responding directly to the question. When the conversation involves input from multiple team members, using Reply keeps everything organized in one thread for ease of reference.
Start a New Conversation
When you want to bring up a new topic in the Channel or start a new conversation, use the Start a New Conversation box at the bottom of the screen.
Mention
As an attention getter in both a Reply or a New Conversation, you can mention someone by name by typing @ and then their name and selecting them from the menu that appears. They will receive a notification that they were mentioned.