I have a text with some ligatures. When I try to delete a part of a ligature strange things happen (all samples in InDesign 5, font EB Garamond OTF/CFF by Georg Duffner):
1. Ligature longs_longs_t. I want to delete the "t" character; placed the cursor after "t" and hit 'backspace'. Unluckily ALL my ligature disappeared!
2. Ligature f_f. I did the same and magically ONLY second"f" disappeared. What a confusion.
I found some info: http://fontforge.org/editexample4.html
"Some word processors will allow the editing caret to be placed inside a ligature (with a caret position between each component of the ligature). This means that the user of that word processor does not need to know s/he is dealing with a ligature and sees behavior very similar to what s/he would see if the components were present. But if the word processor is to be able to do this it must have some information from the font designer giving the locations of appropriate caret positions."
Let's try to select a character in our ligatures:
It looks like "f_f" have "ligature caret' information, "longs_longs_t" have not.
So it is up to font designer. For example Luc[as] writes: http://forum.fontlab.com/index.php?topic=8778.msg29007#msg29007