@ mentioning doesn't work with names with special characters

[ellisonbg]

I just found that the @ mentioning logic doesn't work with names that have some characters:

Example: Pérez

[joadoumie]

@dlqqq -- is this something worth investigating? If so, I can take a look and come up with a proposal.

[ellisonbg]

@joadoumie sure that would be wonderful, let us know if you have questions. You may also have to change things in Jupyter chat, which has the UI for all of this: https://github.com/jupyterlab/jupyter-chat