They are against people forcing people to buy them, they aren't against people taking money for them. It is why many things have donation tabs not fees to get them. Even with that many streamers and youtubers already sell their UI set ups and different WA and Blizzard doesn't do a thing about that. This might push things over the top though and Blizzard with step in.
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God no, there are enough privacy issues with Discord as it is nevermind every so often something like the RF issues on Discord. If they got into add ons the issues of peer to peer would be magnified even further.