Greasy Fork is available in English.
Allows you to write Markdown in the notes, which will be rendered as HTML when the page loads.
< Обсуждения WaniKani Markdown Notes
It seems to be working for me. Note that it requires the web address to be "https://www.wanikani.com/*", so it won't work on preview.wanikani.com or just plain wanikani.com. If you need it to work on any of those, it's a simple matter to change the "@include" lines at the top of the script.
If needed, let's continue the discussion on the Markdown Notes thread in the Wanikani forums.
Huh, weird. I just checked and it's working now. I did restart my browser and all that after installing it.
Anyhow, thanks for making it! One of my favourites.
No longer working? Any chance you could update this script? I really find it helpful to be able to do text formatting.