Conventional wisdom about interstellar comms gets well thumped when a civilisation starts using Claudio Maccone's gravity lens system. The idea is to use one's own star as a giant focuser of radio and light waves. Great telescope, great radio antenna. With about 10 watts we could establish comms with the Alpha Centauri system and get 5 by 9 clarity and good bandwidth. Hard to believe, but that's what the maths says. Of course, there is a bit of a lag.
Our own grav focus begins at about 550 AU out. We'd place a transceiver (nuclear thermal powered I assume) on the opposite side of Sol to the target star system. At the target system we'd do the same. So we end up with a straight line that links remote Tx/Rx - remote star - Sol - local Tx/Rx.
The chief impediment we ourselves currently face is the ability to make such long trips quickly. Once we have that, we could set up radio comms all over the place.
But to the question about aliens. If they are using this mode of communication, there's not a chance in hell that we could detect it.
There's a heavy piece of irony here, as Maccone is chief of SETI.