Blocking

Blocking is when a user prevents another user from using any community-related features towards them. The feature was added on October 2, 2014, and allows individuals to take control of who interacts with them by clicking the Block User button. You can block up to 100 users (previously 50 then increased to 75).

Restrictions
If you are blocked, you may not do any of the following.
 * Send party invites to friends
 * Chat with their friends (their friends can send chat messages to them, but the blocked user will no longer answer back to him/her)
 * Send private messages to friends or other users
 * Send Friend requests to other players
 * Follow their friends to games they are playing
 * Send trade requests to other players
 * Send clan invites to membership users
 * Send ally requests to a group to partner with them
 * Chat In-game with friends or other players
 * Joining private servers