We are having no luck getting the Signal team to acknowledge the issue. The ticket was automatically closed despite activity.
https://github.com/signalapp/Signal-iOS/issues/4916
1. Be aware that a large portion of your storage space might be stolen by Signal.
2. Be aware that this might be a significant security flaw.
3. If anyone can get Signal to pay attention rather than closing repeated tickets as stale, that would be great.