[mtdewcmu]

A single photon can't be seen multiple times, right? So, if photon A goes into Alica's retina, then Bob can't see photon A. If a big, opaque object passes through the event horizon right in front of you, it would absorb or scatter the photons in its path, and you would not see them.

[cyberax]

Yep, I explained it a bit more here: https://news.ycombinator.com/item?id=42299891

[mtdewcmu]

So you don't see _everything_ that went in before you, mostly just the _last_ thing.