How to advocate for this really depends upon how much you care and how much you time and energy you want to put in. The best way to truly get a complete evaluation would indeed be with a comprehensive pull request that implements the definition you want, complete with tests, news, etc., as well as a concise enumeration of the tradeoffs everyone brought to this thread so it’s easy to weigh the pros and cons. But that takes not-insignificant work… and it’s not guaranteed to ever fully resolve. For example, take the attempts at underscore anonymous functions.
If you want a quicker-but-less-definitive go or no-go: If I were you, I’d enumerate pros and cons as best and tersely as I can, drop by #triage on slack or attend a triage meeting, and ask for a quick discussion. The biggest question in my mind is just how “bad” Jeff et al would consider the badness of the | punning to be. Just like what happened in Python-land, though, the first reaction from a core person or two might not be a good predictor of what would happen with a more complete PR/proposal.
Language changes aren’t ever driven by pure democratic simple majorities — not even majorities of the committers, not even majorities of the crew on any given triage call. In my experience, the committers listen pretty closely to any and all objections (both from other committers and the community at large), and the status quo prevails in cases where there are not-insignificant objections. So I don’t have a crystal ball, but I’d temper your expectations (and investments) by re-reading your own post there in that light.