Numderline: OpenType Ligatures for Number Clarity for 4+ digits

This works great with terminals that can handle ligatures. I've used it with Kitty and recently tried it with Ghostty. The author shows several different examples using the fonts to make groups of 3 digits within larger numbers easier to read by adding underlines, grouping numbers closer, bolding numbers, and adding virtual commas. I say the commas are virtual since they are only visible by the font rendering, if you were to copy and paste the numbers the commas would not be included.

The author provides a font patching tool, however mentions that it does not preserve existing ligatures.

This font can be useful when looking at large numbers. I've used it with successfully with Visidata in sheets with large numbers.