Audacious

It would be beneficial for users who are trying to prune their music collections in an organic manner if there was an easy way to rate music as it plays, and see and sort by those ratings, similar to the Marks feature in AIMP.

Not pulling over the unalterable default of rating songs as a 1-star if the user does not interact with a song that lacks a rating would be preferable; it makes the whole rating system much less useful.

A five-star system is, to me, preferable to the up-down rating system used by some competing cross-platform options. If you default to a neutral rating of 3, you have two levels of "like" and "dislike/not impressed", which seems to be about right for grain. Those who want just three options can easily ignore the two and three star ratings, or a different plugin might be used. User-choosable rating scales within one plugin seems likely to cause issues with previously-rated music, but it's not guaranteed.

This is the only feature area I have found that Audacious completely lacks. I am using both the Windows and Linux Mint versions of Audacious.