Ability to 'watch' / 'follow' a message conversation

It would be handy to be able to watch or follow a conversation so that if someone replies to a message that you are interested in, you can be alerted.

Use case:

Colleague A writes a question into a team space. You also need to know the answer to the same question.

Colleague B replies to Colleague A with the answer.

If you could follow the conversation, then you would be alerted to the response.