Oliver Kühn It's really a matter of preference. Sometimes ligatures do help legibility, sometimes they can just look cleaner. I agree that every symbol has its meaning by itself, but specific combinations of symbols have distinct meanings too, and since it's mandatory that the replacement symbol takes exactly the same space as the symbol it replaces and that more often than not it's fairly evident which the original symbols are, I don't see where's the problem. After all, it takes no extra steps and no special effort to make ligatures in a font optional (ultimately the original symbols must also be there).
