BNHA Theory
{I know this is a long read. There is a TL:DR at the bottom.}
OK, so here me out. First, I really don’t think Izuku is quirkless, I don’t think he ever was.
Before you start, No. this isn’t about that theory ‘All for One is Izuku’s dad and stole his quirk.’ No.
This theory actually has nothing to do with All For One.
This theory is based on if Hisashi Midoriya was just a regular person with a quirk that let him breath fire. I pull a Deku and started doing a deep dive on what the quirk, Fire Breathing, could be and possibly be expand too. Breathing Fire reminded me of Dragons, and the line of thought of Hisashi Midoriya’s quirk not being fire breathing but instead a small draconic mutation quirk.
All Might explained that people update their quirk status more than one would think, especially heroes. As they are continuously pushing their quirks to the limit and as a result learning new things about them. Something that a civilian wouldn’t do. (Given the whole ‘illegal to use your quirk in public’ law). Civilians don’t really have the ability to experiment with their quirks, so Hisashi likely never pushed his quirk beyond the basis of fire breathing. Inko, herself, confirms that both she and her husband are fourth generation quirk holders. Statistically speaking it is extremely unlikely that Izuku would be born quirkless. It is more likely that he had a small unnoticeable quirk. something that wouldn’t be that strange in the BNHA world, there are many people shown who do not have a quirk that is visibly obvious.
But, if Hisashi Midoriya had a Mutation Quirk and said mutation was passed onto Izuku, it changes so many things. It would explain why Izuku never seemed to ‘gain’ an ability, after all he was born with it, so there would be no change. This idea could also explain Izuku’s x-ray. Mutations change a body physically. I don’t think the toe joint test would be all that reliable when you have a mutation based quirk. Maybe Izuku has two joints for extra balance, but majority of the mutation effected something not seen in an x-ray. Like, perhaps, his brain?
{Also, do you really think that Tsuyu Asui would have a normal x-ray? Do you know how many toe joints a frog has? I’ll tell you this, her pinky toe would defiantly have two joints, if not more. Don’t see any doctor’s claiming her to be quirkless.}
So, what if Izuku was born with a draconic mutation quirk? Something small, like his father’s mutation.
Maybe something like hoarding?
Izuku, in a way, hoards not only hero merch, but also knowledge on Heroes and Quirks.
What if Izuku’s quirk has him hoarding information, this is physically represented by his notebooks?
TL:DR - Izuku Midoriya could have been born with a Dragon Mutation Quirk.
