Just use EDN.

Not only it supports comments and trailing commas, it allows to avoid commas at all (they are simply ignored by EDN). Commas indeed are just redundant and incur visual noise most of the time.

    [1, 2, 3]
    [1 2 3]       ; much better

The spec: https://github.com/edn-format/edn/blob/master/README.md

Examples at github (261k files found at the moment) : https://github.com/search?q=path%3A*.edn+&type=code

Github search only shows the first 5 pages of results. To extract more results split the search with more specific path qalifiers:

    path:*a.edn
    path:*b.edn
    path:*c.edn