Steps to reproduce:

1. Go to en.wikipedia.org (or any other language-version of Wikipedia)
2. Enable 2017 wikitext editor in Beta settings
3. Open any article and click the Edit tab
4. Make an edit and click Publish changes
5. Enter an edit summary
6. Click Review your changes

Expected result: below "Preview of edit summary:" there should be a preview of the edit summary

Actual result: below "Preview of edit summary:" is just a placeholder ($1) instead of the preview