Sorry if this sounds like a dumb or re-hashed question. I have several scopes with mounts that place them right at the front sight height, an absolute co-witness. I did this so my cheek weld and position was identical when using iron sights.

I completely understand that in practice, at low power the front sight is only a blur, and at higher power, it is invisible.

But if shooting at 100 yards or more, even though you cannot see the front sight post, it is still blocking the crosshairs' intersection. Does this have any effect, or does the curvature of the lens "fill in" the missing image?  The view must have some fraction of missing image, right?

This is just a theoretical optics question, I normally shoot my ARs at the 100 yard range I have access to, and get 2" groups with the bulk mil-spec ammo I shoot. Just curious for a technical explanation.

My buddy talked about this yesterday and I hope someone explains cause its a question I have too.

It has no effect whatsoever on you crosshairs or down range accuracy.  Period.  If you are using any magnification it is not in focus and it's presence does not change your point of impact. Period.