Seemed like an interesting idea so after some sanity checking decided to see how feasible this would be on kitty.

Interestingly enough the kitty author has declined a feature request similar to this couple years ago in https://github.com/kovidgoyal/kitty/issues/7511 but the approach here seem to have not resulted in any of the major pains he was expecting in that message. It is valid point that implementing something like this on a single terminal might not be worth it, but now we have poc available for two major ones I guess?

Anyways, branch and write-up available here: https://github.com/errnoh/kitty/blob/cell-borders/CELL-BORDE...

(The usual disclaimers apply: all of the actual code is AI written)