[jerf]

Compressing increases bandwidth, which is forever going to be at a premium. If you want to improve reception reliability, you put error correction on top of that. This is all off-the-shelf tech here on Earth, to say nothing of what aliens can come up with.

"Besides that, I can't imagine radio being used for interstellar communication at all. It's fine for "Is anyone there?" but unless your aliens live at geological rather than biological rates, it's far too slow for almost anything else."

Well, it's the fastest thing available unless you're basically willing to hypothesize magic. Anyone willing to do so is welcome to do so, and I'm serious about that; I just advocate that you be aware that you've switched to advocating magic. There's a difference between reasonable speculations based on real physics and arbitrarily advanced engineering, vs. new physics that despite all our research we still have little more than a whiff of, if that, and keeps crawling into ever more exotic energy domains to even peek at.