This can be a very witty placement for Mercury, even though they might not be the most talkative of people. Some are very skilled at delivering witty one-liners.
This placement is great for conspiracy theorists for there can be a tendency to take a somewhat dark, cynical or unflinchingly honest view of human nature. Often there is an interest in psychological matters, if not academically then certainly in simply trying to fathom what makes others tick. There is an interest too in researching death, sex, medicine, energy, the occult and potentially all of lives mysteries and taboo topics.
Although this placement can indicate a person of few words-someone who does not give away more than what is necessary-it is often descriptive of someone who when they do talk, speak with great passion and intensity. So much so, than others might loath to disagree.
Mercury here can indicate a tremendous mental stamina: the person who is still awake and studying while others are tucked away in bed. Or it can be the person who understands and can illustrate the notion of mind over matter. Once the mind is put to something, then anything is possible. But often Mercury Scorpio people can have obsessive thoughts gripping them so they learn to control their thinking patterns in order to harness these more negative patterns.
They take their time before allowing friends into their life and will usually test them, but once the bond is there it will be usually very deep and loyal. Jealousy and sudden reversals can be a strong feature in sibling or friendship relationships.
Something more to read...
Soothing Herbs for Difficult Times
How the 12 Signs Fall In Love and Act in Love
Planets on the Ascendant
Retrograde Planets in the Birth Chart. Curse or Something else?
12 Faces of the Zodiac Signs
Black Moon Lilith In the 12 Signs
The Most Passionate and Powerful Relationships of your Life