The input box for conversations requires 2 or more characters to start a user lookup. If you type a single character username in, the field will also remove your input.
The field should attempt verifying if the username is correct before removing it.
Optionally, if someone inputs a single character it can search for single character members, which well, it would end up only finding the user you are looking for.
Edit For Moderators: Sorry for the original topic, it ended up being a mistake on my end.