In the modern age Latin script, the only acceptable ligature is "fi" in a proportional type, because the top curve of the F usually comes very close to the dot of the I already. For the rest, they're totally useless because we don't use moveable type anymore.
Well, I also tend to enjoy programming ligatures, such as != becoming ≠ or => becoming ⇒. (but in a size proportional to the pair of fixed width characters, see https://github.com/tonsky/FiraCode )
But then I don't inflict them on anyone but myself and people who look over my shoulder...
