Issue Summary

When reading PR notification emails in text, not HTML, @mentions are rendered as hashes and are unreadable.

I am reporting on behalf of Dan Kortschak (dan@kortschak.io)

Steps to Reproduce

1. Open a PR notifications email with @mention
2. read in text-only email client

Expected Results

@mentions are displayed as handles, not hashes.

Actual Results

Workaround

Read email in a HTML-capable rich client.