Steps to replicate the issue:
- Use the new 2017 wikitext editor
- Change your display language to an RTL language
- Visit an article written in a LTR language
- Open the wikitext editor (and edit)
- Preview your edit
What happens?:
The article text is RTL rather than LTR
What should have happened instead?:
The article text should be LTR, which would be consistent with the editor itself and viewing the article
Software version (skip for WMF-hosted wikis like Wikipedia): master
Other information (browser name/version, screenshots, etc.):
 |  |  |
| Article being viewed | Article being viewed | Article being previewed |
| LTR? ✅ | LTR? ✅ | LTR? ❌ |