I just encountered an unexpected behaviour of SP online working with the local ms office.
It looks like if someone opens a document (i.e. docx), the local word instance doesn't care about the user logged in in SP online.
Let's say there are 2 users, Marc and Tom. Marc uploads a document and restricts the access to readonly for Tom. Now Tom only can read the document, even in MS Word. If he loggs in as Marc and tries to open the document, I would expect the document to be editable. In MS Word online it is, but as soon as Tom (now logged in as Marc) opens the document in MS Word on his computer, it's readonly again.
I suppose that's as designed. But does anyone know the technical background of this? How does SP authenticate users against the local MS-Office?