This is a feature request stemming from the question below:
It would be beneficial to offer a "Block User" feature that allows users to block other users at a title level. This would help developers support cross platform gameplay across major platforms.
Xbox Best Practice:
XR-007 Cross-Network Play, Data Usage, and Companion App Interactions .. In addition to these requirements it is best practice to provide per-player communication block functionality for non-Xbox Live users. ..
(This will likely change due to Fortnite issues being reported pertaining to blocked users.)
The current solution is to have blocked user ids stored on user data and checked before and after matchmaking has concluded.
This would also support developer systems like player messaging, and chat.