Some players are making abuse of emotes, “Greetings”, “Well played”, “Sorry” etc.
There isn’t any option to ban a player (not to meet him in future games).
However, there is a function that can mute a player so you won’t see and hear his emotes.
When being in a game, right click the enemy hero and click on “Squelch”. This will do the job.
You can un-mute him by doing right click again and “Unsquelch”.