If it's not obvious how this could be achieved with overstrike, basically the idea is that you could draw text on a cell then overstrike the cell with 1/8 block characters for the 4 edges characters (U+2581 & friends) to create a border around the cell.
Edit: HN stripped the characters in question from my comment
If it's not obvious how this could be achieved with overstrike, basically the idea is that you could draw text on a cell then overstrike the cell with 1/8 block characters for the 4 edges characters (U+2581 & friends) to create a border around the cell.
Edit: HN stripped the characters in question from my comment