I can't think of a good reason to have such a ligature.

Serf. And no I don't think there is one. Maybe in a script font.

One reason to have a ligature is the same as one reason to have serifs.

hhp

@hrant Decoration? Better "word image"?

Bingo on #2.

hhp

Not sure what nice is but this family's got them.

At least in Spanish you can use it in words such as Orfeo, Surfeo, Garfio, Morfeo.

Just don't use it to set Barſtow.

hhp

Kerf, nerf, turf and, lest we forget, Ferd Burfle...

Everybody’s gone surfin’…

Really, an rf lig? Barf! ;-)

Not a ligature per se, but in the project I'm working on at the moment, I've added contextual alternates for "rf" ant "rt"

Good move.

hhp

A connected /rf/ would be better, imo. At least makes for better spacing.

@Hrant "Bingo on #2."

Wonderful. And what do you think the "rules" should be for ligating to better word shapes?

@Sii "Really, an rf lig? Barf! ;-)"

Butterfly head, it's on a billion windows machines, should we recall it?

@BV "At least makes for better spacing."

Bert, there's and rt lig too ;)

I once gave a talk in Thessaloniki about the hidden benefits of ligation, including aiding readability. At least one person though thinks that talk was crap. :-) But he's (still) a friend.

I haven't thought it all through, but I think the best basis would be to go through the lexicon of a given language and for word pairs (or more generally, sets) that have convergent boumas use ligation to diverge them. But it has to be consistent.

For example in English, for "guest" and "quest" the latter might get an "st" ligature but the former not.

hhp

@BV "At least makes for better spacing."
Bert, there's and rt lig too ;)

?
The spacing on that one is still a mess. I'm not sure what I plan on doing with it.

For example in English, for "guest" and "quest" the latter might get an "st" ligature but the former not.

Interesting idea. Wouldn't that be distracting in some cases, at least at first. While that would change the word shape for "quest" in this case, perhaps for better recognition, but it would only really work if everyone made the same choice. What if one designer thought the former should it? I'm not arguing that it wouldn't improve things, but it would only to well if it were adopted by many people.