Just checked and Spotify sorting isn't stable, either. Presumably this is because, as with most apps based on a database of some sort, there may not be a "mater

Just checked and Spotify sorting isn't stable, either. Presumably this is because, as with most apps based on a database of some sort, there may not be a "materialized" in-memory data model that one would sort, but the column to be sorted by is passed to the backing database as a part of a query. The app could, I guess, remember the last few sort-by columns and craft the query accordingly. However, insofar as most people desire the ability to sort by multiple columns, they'd likely also want a more intuitive UI than clicking the columns in the reverse order of priority. A few years ago I participated in developing a datagrid component where you could add columns to the sort order by shift-clicking.