I created this page in hopes of spurring a discussion.
Maybe there should not be a set universal reference frequency, but it could be advantageous to develop a sort of notation proposal so that musical pieces can be shared and played in the same tuning system, including reference tuning.
For example, if I play a song with the chord changes I - IV - I - V in 12-EDO with two other musicians, I can specify the key of A, tempo of quarter note = 120 bpm, and A4 = 440 Hz, and that should ensure that everyone in the band can play through the general idea of the song, even if they never met prior. If I leave out the A4 = 440 Hz part, chances are pretty good that it'll be assumed anyway. However, if everything is as I just said in the example, but I use 19-EDO instead of 12-EDO, and leave out the A4 = 440 Hz information, then there might be a problem. Most likely, at least one musician will tune to C instead of A, since, from my understanding of a discussion I saw on the Facebook group, microtonal musicians use middle C instead of the A above middle C as the standard, even though >50% of the rest of the world uses A.
So, would it be too cumbersome to write C = 261.626 Hz?
That still leaves open the discussion regarding other tuning systems. I honestly don't even know where to start with something like 5-EDO. Pick a note and tune it to a specific frequency, I guess.