I understand editing the service extensibility config directly is not supported/recommend, and therefor this issue shouldn't be expected to impact any environments under normal circumstances. However I found some interesting behaviour that occurs when an AdapterConfiguration object in the Unify.Product.IdentityBroker.AdapterEnginePlugInKey.extensibility.config.xml file is given a duplicate "AdapterId".
When attempting to start the service with an incorrect configuration like this, the service fails to start which is expected, however the entire Unify.Product.IdentityBroker.AdapterEnginePlugInKey.extensibility.config.xml file is also cleared and saved in the process. Clearing any other configuration that may be there. I'm unsure if this is intended behaviour, but figured I would log this here anyway for your consideration so the service would simply fail and not save over the configuration.
UNIFYBroker version 5.3.1
Customer support service by UserEcho