Adding people to messages

i have had a problem when i would send a group message and i accidentally made a typo in someones username and the message. so i have to make a second separate message to to let them know whats going on. would it be possible to add a feature so you can add people to a conversation after you have sent it?

Or another possibility would be to have the system offer suggestions if you type a name nearly correctly. Some usernames are hard to remember so I think this would be helpful, plus it would solve marcoxa's issue.