When a <10k user browses to a deleted question, they are told whether the question was deleted voluntarily by its author, or by others moderating the site (i.e. "for reasons of moderation"). This information is considered public and is visible to all users.
The only way to check this, though, is to actually load the question. This information isn't made available through the API or SEDE. Can we please make this info available through those means?
One use case for having it available through the API is that I've noticed some cases of spam in which a spammer posts their spam question and deletes it shortly afterwards, and then undeletes it at some point in the future, when it's old enough to be off the home page that no one sees it. The programs written by Charcoal can't tell if a question was deleted voluntarily as they use the API, so when a post is deleted they just stop watching it. If the bots knew that a certain caught question was deleted by its author, they could keep an eye on it and alert if it gets undeleted.
Can we please make the information as to whether or not a deleted question was deleted voluntarily by its author available in the API? I'm aware that in certain cases it may misidentify posts, such as posts that were voluntarily deleted by deleted users, but this isn't an issue for the use case I've pointed out (deleted accounts can't restore their own posts for obvious reasons).