It says:

"An engineered galaxy, in which almost every Sun-like star within that galaxy had been enclosed within a Dyson sphere would have a very high infrared emission, low optical luminosity and a high galactic stellar rotational velocity in the case of spiral galaxies; or a high velocity stellar dispersion in the case of elliptical galaxies.

According to Annis’ calculations, one such macroengineering signature might be that you would see only about 100th of 1% of the light from the galaxy. “If you were to see obvious dust clouds around a candidate galaxy in the infrared, then it could be a dusty starburst galaxy where the dust is very clumpy and you can see ongoing star formation,” he says. “But if you got an infrared galactic image that was completely smooth with no lumpiness, that’s an interesting object.” To create such optical dimming on a galactic scale, a KIII galactic civilization would have needed to colonize almost every Sun-like star within its galaxy.

“We can already rule out certain kinds of civilizations,” says Werthimer. “I don’t think that there are civilizations out there that harness the whole power of their galaxies or cluster of galaxies. My guess is that just from the astronomical data on file we would have discovered such a civilization by accident.”

So either ETs don't behave this way on a galaxy level, or ET isn't out there. The other links you have point out that ETs could behave differently, an obvious point IMHO, but it's still an interesting piece of information.

Thanks for the post!