With how the [COMM frame](https://github.com/quodlibet/mutagen/blob/f3077306f3ac28c62d6aaed71cda22ecf530de5c/mutagen/id3/_frames.py#L1110) is [added using the `HashKey`](https://github.com/quodlibet/mutagen/blob/f3077306f3ac28c62d6aaed71cda22ecf530de5c/mutagen/id3/_tags.py#L284), there's an issue when saving the value to id3v1 due to it [expecting only the `COMM` key](https://github.com/quodlibet/mutagen/blob/f3077306f3ac28c62d6aaed71cda22ecf530de5c/mutagen/id3/_id3v1.py#L175).