I play on an RP realm too, Feathermoon. I have actually seen a lot more RP lately than I have in a long time, especially in the Purple Parlor in Dalaran, which seems to be there for no other real purpose.
I think it just varies by server. I know that on Feathermoon, RP in the global channels like General just doesn't happen. At the most, you might see someone phrase a question about a quest or something in trollspeak. RP by emote or in 'say' does happen. I've seen guilds do initiations in RP form in the Ruins of Lordaeron.
All that being said, I can't count the number of times I've yelled 'Lok'tar Ogar!' when Ony or Nef were killed, or when we'd just succeeded at a city raid. Not really serious RP, I know, but it does add some flavor.
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