REST API question: finding out if a user has subscribed to a page
I'm about to write a little Browser Add-On that hooks into the COYO web frontend with a button and allows to collect all the comments of a blog post. We need this because we offer raffles for all employees via a blog post and the employees need to make a comment below that post to be able to win.
However, to be eligable the commenting users also need to follow our page. So I want to test for every commenter if he/she follows/has subscribed to our page.
In the REST API documentation I found this endpoint:
/users/<user ID>/subscriptions?targetId=<ID of page>
However, this only seems to work for my own user ID. If I use a commenter's user ID I always get a "404" result.
Now, because I'm writing a Browser Add-On here I'm "only" authenticated via my own user account agains the API (I'm getting the neccessary token for each REST API call from the
/web/authorization/token endpoint; this works fine).
Is there any way in this constellation to check if a user follows a page? Or is it by design that I can only check for my own subscriptions when using the REST API this way?