Hmmm. So RadioAstronomer has an exhaustive list of all possible types of naturally-occurring signals? Wow.
I don't see how this is different from what ID does.
Having done the time at a radio telescope myself: Yes.
The last real big false positive? Pulsars. A regular signal that keeps nearly perfect time, with a very regular spectrum. They were detected nearly 40 years ago. That's the last serious near miss for LGM hunters. Though RA would know more than me. I tended to look at more exotic items in my line of work.