It seems the behaviour is fundamentally different depending on the setting of
Show people added from movie credits. Selecting this setting causes all invisible movies to become visible, and then the delete behaviour is as I describe above. If the setting is not selected, then, according to
Anson's testing, the behaviour is analogous to how delete and ctrl-delete work for movies.
Mumin, I suspect you have checked
Show people added from movie credits (at Preferences - People). If you're not interested in recording information about any people (other than their name and which movies in your collection they appear in), you could deselect this option. It won't change change any of the records already recorded, but will new people (from new movies added) will be invisible and no unnecessary information will be added. You'll be able to "delete" existing people to make them invisible, but that won't change any of the information already recorded.
I do not recommend you do this, however. It's easy to feel PVD is collecting information about too many people. But if you want the information (particularly the filmographies) for
anyone, there's really no choice but to let the program get the information for all of them. You can limit the number of people by selecting
...Except actors (from main page only) in the plugin configuration and
Do not add people from awards... on the plugins page.
Nostra, I think you should consider changing the delete behaviour, but I haven't thought it through. I suspect you knew what you were doing when you originally coded this, and nothing has changed.