This was brought up in NAT as well, I've been thinking about it since then
Generally:
People think it'd be beneficial to have some way to indicate it
However, perf. does not seem like the ideal way to do this to me.
- its meaning may be ambiguous
- when it does and does not apply can be hard to define, and would be hard to follow on the broader scale of all of osu!. It seems like a great idea for small set cases, but trust me, if it's not water tight when it does and doesn't apply it will be very confusing for others and other discussions.
- current allowances do allow for formatting with multiple artists already, but some points were brought up about it not being clear enough.
So instead, I think broadening the scope of an existing allowance would be better.
This one in particular:
For Remixes/Covers, the original artist may be used in the artist field, as long as the title field is modified to clearly show that the song is remixed.
I think could simply be changed to
For Remixes, Covers, or Performances, the original artist may be used in the artist field, as long as the title field is modified to clearly show that the song is not the original.
This would allow stuff like
Composer - Title (Musician's Performance)
Within already existing allowances, and without adding an extremely niche+specific guideline.