What I didn't understand about these pings is wouldn't their wavelength be massively lengthened by the time dilation? How did they even receive Miller's signal if it was redshifted ~60000 times?
That is an excellent point, I didn't even consider that. It's possible they were listening on the correct frequency to receive it, since they knew the redshift was going to happen, but that just leaves more questions as to why they didn't then realize that it definitely couldn't repeat.
