@DownPW yeah im having the same issue.....
Rename the references to the username
When changing a username
The mentions remain ownerless
I am asking for a plugin that solves the problem
That when the username changes, along with it The mentions change to the new name
The idea can be improved
That when the previous name is mentioned, in the combination of @, the new name will be registered as a mention.
On further thought
Allegedly this is related to a plugin that allows mentions by @
That's why I mention the @julian
@chez please open this as a feature request against the mentions plugin GitHub repository