Poultry Talk Ontario (pto.ca)

I'm guessing it's hereditary?
Not the dad of this chick but I guess you would call it the grandfather of this chick had an inverted comb

Weird! I've never seen a comb like that before.

Yes it is heritable, but I was never able to find out just how it was inherited. I had a Cornish rooster with an inverted pea comb, the hens can have one too but it's harder to see. My best rooster had this comb, and I decided to cull him based on that comb, because it can get infected- it's a disqualification for the SOP and can be problematic for the chicken. Grant Bereton of Wyandotte fame recommends not breeding a bird with such a comb.
One breeder I corresponded with said he had bred a rooster that had an inverted comb, and got some chicks with and some without, but he did not do any sort of trial that would indicate whether it's sex linked, dominant, recessive, or neither.
Best not to breed him unless he's superb in every other way based on what others have told me.

Would that be called an "inny" comb?

Wow I have never seen one either, and yes if the grandfather had one it would be hereditary.

@ Schnookie, thanks for my morning laugh!!!