For anyone still following this thread ...
I have found that including the following in the CSS file makes ligatures display in kepubs for me. Of course the results are only as good as the font you're using:
Code:
text-rendering: optimizeLegibility;
or alternatively:
Code:
-webkit-font-feature-settings: "liga", "dlig";
I don't know if one has a significant advantage/disadvantage over the other. I'm currently using the first one to see how it goes.
I don't want to add special code to my calibre master version epubs so I applied it using the kobo_extra.css file of the
'Modify CSS' option in the calibre KoboTouch/KoboTouchExtended driver. As I don't know what (if any) effect this code would have in the Adobe renderer when added to a standard epub CSS file I made sure the code would only ever be used in kepubs by using this code in kobo_extra.css:
Code:
body > div#book-columns > div#book-inner {text-rendering: optimizeLegibility}
Here are a couple of screenshots to demo the slight difference with (left) and without (right) ligatures.
ETA: I should probably also add that this was all done on a KA1 with fw 4.1.7729. I have no reason to believe it won't work on earlier models with earlier firmwares but I haven't tested it because my other Kobos only contain standard epubs at the moment.