I think WoW RP is sort of a Reeses Peanutbutter Cup type of thing:

You got RP in my WoW.

You got WoW in my RP.

..Together they taste great!

In other (less inane?) terms, it's not that WoW is a superior format for RP, it's that people who like both WoW and RP want to mix them, limitations aside.

Squidpuppet put it pretty well, so I'm just gonna chime in to agree.

I've always been fond of old school chatroom and forum RP, but getting a bunch of nerds together in one room to roll some 500-sided dice is a bit much for me.

WoW is definitely limited, but having a natural attachment to a character you've played for years and a bit of imagination makes it hard not to RP a little. Like squidpuppet said, I enjoy RP and WoW, so why not mix the two?

WoW is as much a game of the imagination as tabletop RPGs -- except in WoW, you can actually SEE your character, go into battle, choose your fights, type what you want to say and not have to worry about hurting your voice with attempting that Dwarf accent. It's in front of your face, not all in your mind.

Playing & speaking "in character" is just as much RP as collaborative storytelling; not all RPers are into the storytelling. Some of us just want to play...um..."regular" people of our race (well, as regular as you can get in a fantasy setting, anyway). There's nothing like yelling battlecries as you charge in, or tossing off custom insults to taunt monsters off my buddies...or in my gnome's case, giving long-winded technobabbly explanations to my guildies as to why there's a Green Glowing Melted Mess out back the guildhall where the outhouse used to be.

"Good sir, who is this Chuck Norris of which you speak? I'm certain I never meant to offend his mighty chin."

There are plenty of ways to deal with griefers and the limitations imposed by game mechanics. In fact I'd argue that in many cases limitations only serve to spark the imagination. A player's ability to adjust on the fly is relative to their creativity, but quite often people can surprise themselves and other people.

I think this ties into the point of this article. As I stated in a different comment I think mixing up role play and getting away from the serious business is not only healthy but necessary sometimes. That being said, it's also the case that limitations make for better role play, or writing, or any form of creativity. This isn't the actual point of this article but I think the two concepts are related.

What others have said; it's not better than tabletop, but nobody's saying you need to pick one or the other. You can indeed have both. For me, it's the icing on a cake: WoW just isn't as much fun without a bit of extra immersion to give things a personal context.

I also think WoW role-play shines most in comedic scenes, to be honest, but I have had genuinely compelling and moving dramatic scenes.

Also, tabletop requires a DM. Freeform WoW rp does not.

"Playing & speaking "in character" is just as much RP as collaborative storytelling; not all RPers are into the storytelling. Some of us just want to play...um..."regular" people of our race..."

That sums it up 100% for me. I'm not into the whole storytelling thing ~ I don't want to hear the backstory of ever person I encounter IRL, and I don't want it in WoW. However, I am always tickled to run across other players speaking and behaving in-character when I'm on an RP realm.