You can do this directly from your 'Blocking' settings. To get to 'Blocking' move your cursor over 'Home' (this will look like your avatar if you are using a condensed navigational menu) then select 'Settings,' then choose 'Blocking' This will lead you to this page: ( https://www.chess.com/settings/blocking) and you will see a form where you can enter the name of a user to block.
You can also block someone directly in Live Chess by hovering over their username. This will reveal a menu with a number of options, one of which is to block them:
Once blocked, a member cannot do any of the following:
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