I asked a question at
Can an incorporeal creature occupy the same space as another creature?Can an incorporeal creature occupy the same space as another creature?
And a mod closed it as "too broad". It clearly is not too broad and there is already an answer to it and a comment lead me to a book that can answer it even better and completely in a short space, but I can't even put that answer there now. (it also invalidates the current only answer, which I foolishly upvoted at first and now cannot downvote) The mod told me to post here, otherwise I wouldn't for a simple issue like this.