[jeffalyanak]

Yeah, I generally do _not_ like programming-oriented ligatures, but the one for todo is sort of interesting.

However, many editors can accomplish the same goal by highlighting or changing the text colour of todos.

[globular-toast]

Emacs package for that (highlights others like FIXME etc): https://github.com/tarsius/hl-todo

You could make it have the outline thing if you tweak your theme. I wouldn't start installing or hacking your fonts to get this kind of stuff.