After @kleinerpirat’s remark on IDE integration, I wondered if it could be possible to integrate Anki’s template language with Emacs’ web mode, as it already supports tons of similar template languages. So I contacted the author of web-mode a few days ago, and he kindly accepted to do that. Now, back to the present, the support is real! So far, you have to edit .anki files for it to automatically catch up, but for those who use org-mode in conjunction with anki-mode, it’s probably possible to setup an org-babel block for the cards.
Anyways, any feedback would be greatly appreciated, here or directly on the dedicated issue of web-mode.
Also, I provided the author a short file containing most of the features of Anki’s template language here. I based it on the documentation of card templates, but maybe some are missing. Feel free to directly contact the author to provide more feature requests!