My idea project files live in the toplevel directory of my project.
As such they are shown in the project and can be opened in the editor
(as plain text, not XML).
first, this looks dangerous to me.
second, if I do textual searches, the results include what is found in
the idea project files which is not what I am interested in ;)
so, search and replace loks even more dangerous ...
I suggest to add the idea project file extensions to the IDE ignore list
(I've done that).