You do inevitably start to identify quite personally with a character after spending a year or more inside her head, so it's a bit nerve-wracking to put the story out there and realise that other people may in fact not share your feelings about her. And to remember that this doesn't necessarily mean that they are judging you, the author -- although, to be honest, unless you were consciously trying to write a villain character (and generally speaking even if you were, since the aim is to show the villain as someone who makes sense from their own point of view, e.g. writing Lucille from "Crimson Peak"...) if readers have a hostile reaction to your protagonist it probably does mean that you failed :-(

But the 'Phantom' fandom does have a long history of people writing self-insert and/or fix-it OFCs whom nobody but the author is particularly invested in, and most of them do tend to get passed over by the readers on principle. So having people actively pick out your OFC protagonist as the element that they liked about the story is a tremendous relief (and compliment!)

Ironically Jos Perlman of "The Daaé Case" actually was a lot closer to being an inadvertent self-insert...