When I try to delete the entry it basically says that it is in use of itself (or something like that?):
Not quite by itself. [:)]
On the one hand, you have "the dyndns->rules configuration". That's basically a global container containing anything related to DynDNS.
Then, you can have multiple "dyndns->dyndns objects" that you can edit and switch on and off. These objects are used by the dyndns->rules configuration. You can also see that in your screenshot, the info button says: "Used in these configurations: NetworkServices->DNS->DynDNS."
So, what the "WTH-Popup" [;)] is trying to tell you is that the (individual) object, possibly one of several, is still used by the DynDNS configuration at large.
But you are right in so far as that goes without saying: Each and every dyndns->dyndns object is always used by the dyndns->rules configuration, so there is really no point in explicitely warning you. There are several such container nodes in the configuration doing nothing else but collecting all objects of one particular class and type. I have now marked all these pure object container configurations (35 different containers all told!) to get rid of this type of warnings in those cases where they are trivial.
In case you are curious what your finding triggered, look at the file /var/confd/res/meta after upgrading to 7.480. That's the format description of the main configuration tree. The 35 pure object container nodes are now marked with the new optional boolean flag "_delete_quietly".
