The part of the string before the comma may do something interesting; further reverse-engineering may reveal its purpose, but what I'd like to know more is what application(s) actually use read: and for what.
That somewhat makes sense, but then one wonders why it wasn't restricted in the same way as file:// or the usual http(s):// protocols. Of course "Reading View" could've been implemented in a simpler way that people were accomplishing the same thing before (either saving the pages or their URLs to a centralised place), but leave it to MS to reinvent it in the form of an overly complex and insecure solution...