Using the @ symbol resolves usernames when used in PR suggestions

Issue Summary

When the @ symbol is used in a PR suggestion, such as when specifying a Java annotation, if the phrase following the symbol matches a username - the token will be rendered as the full name of the user.

Steps to Reproduce

1. Create a user with username 'test' and full name 'Test User 123'
2. Navigate to an open pull request with code changes
3. Make an in-line comment with the following value:

   • ```suggestion
     @Test
     ```

Expected Results

On saving, the suggestion renders using the expected "Test" annotation

Actual Results

On saving, the suggestion renders incorrectly with 'Test User 123' and appears to suggest that the code be changed to 'Test User 123'

• Note: Applying the suggestion automatically in a new commit will still make the appropriate code change in the underlying commit, and will NOT use the full name of the user.

Workaround

Change the username of the offending user to not match the desired annotation, or change the annotation to not match the username of an existing user