I wrote in an email:
Il lui coûterait sans doute de l’avouer, mais sa maîtrise de la cuisine japonaise est assez médiore...
I haven’t given it much thought until now, but when « il/cela/ça » serves as the dummy subject referring to the part after « de », I’m not completely sure when to use « il », as opposed to « cela/ça ».
The difference between « cela » and « ça » is about formal vs informal, but how do these two compare with « il »?