I think it depends on who is being complimented, and who is doing the complimenting. When someone compliments me for being articulate, I don't think they're just saying it because they expected me to be a mouth-breather. I think it's a genuine, if misapplied, compliment. But I might think otherwise if I happened to be a black man whose articulateness kept getting pointed out by white people who always seemed to mention how surprised they were by my articulateness. I'd start to wonder pretty quickly just why they were surprised, and why they felt the need to point it out as something notable.
This happens to me. It is annoying. But really, I can't think of many situations where it's worth pointing out that somebody is articulate as a compliment. Maybe if they are truly some kind of word wizard, I would get it. But I think most people who are complimented for their articulateness simply speak with proper grammar and a somewhat expanded vocabulary.