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Kind of contrived, but if you're sending a signal from some other planet to our planet, depending on the geometry, there will be times of the year that our local star is in the way of photons.

Also, if you're sending out photons from a planet, chances are there's a local star nearby. Stars tend to be a broad-spectrum photon source, which is going to make it tough for receivers to decode the intentional signal.

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Which is more difficult:

(1) Putting a telescope in space

(2) Focusing and detecting very high energy neutrinos

This is especially the case when photons will have, what, 15 orders of magnitude less energy than the neutrinos?

> Which is more difficult:

This is why I always search for my keys under the streetlamp, even though I dropped them in the unlit field nearby.

That said, putting a telescope in space is easy; we've done it several times...

But, can we filter photons intentionally sent from some far off solar system out of the stream of photons coming from their local star?

Yes. It's been proposed for SETI inside our galaxy too, and could be done with current technology (at least, receiving).

It would be VASTLY easier than using neutrinos.

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