One possible extension of this is to erase the original subtitles using something like gimp-resynthesizer's Heal Selection, and then replace them with translated ones, all automatically. (I've redrawn the video frame from the post[1] so you can see what I mean.)
Using a 2d image resynthesis algorithm is sub-optimal for video. There is basically no chance of it picking the same result every single frame, you will see a flickering shadow of weirdness where the old characters were.
You have lots of infomation of what image should be there; You have motion vectors signaling when an object or background has moved into (or out of) a blocked area. Or a maybe the motion vectors indicate object/background is stationary and you can use infomation from before/after the subtitles to fill it in.
I'm not aware of such a 3d video resynthesis algorithm existing, but it should be possible.
[1]: https://static.linestarve.com/ext/ycombinator-news/itm144408...