This seems like a potential minefield if implemented naively.
e.g. someone could make an account with your username, implement a troll campaign, then walk into someplace like !chapotraphouse@hexbear.net and cause not only themselves but YOU also to receive hundreds of DMs over the course of WEEKS and WEEKS, with little to no recourse to stop it.
But... admittedly the likelihood of that seems extremely low (for a normal person), so if it would be too much work to try to prevent, then even in that case perhaps that possibility should not stop the rest of us from having features useful to those capable of existing in a more polite society?