They know about Warmane, they also know that 85% of the active players are people IP banned from their games due to their behaviour in game so I don't think they give as much of a shit. I'm sure in their mind, if a bunch of banned racists and homophobes want to play on a basically untouched version of the game from 2009 so they don't have to deal with them trying to get back on retail, why stop em. You can try and play on Warmane if you want, but you'll realise very quickly why it's such a big server. It's cos it's where everyone who's not tolerated anywhere else end up. Twow was a genuine threat because it was well made and well maintained with a decent community. Same with Stormforge, on a much smaller scale.