Ebertin in The Combination of Stellar Influneces, is a good supplemental resource in this respect. His thoughts are as follows:
A convincing speaker, the power to influence the public or the masses, a critic, a writer
On the other, less positive side he goes on to say that Mercury/Pluto combinations can also produce,The art of persuasion, suggestion. An amazingly sharp criticism, intellectual triumph over others, slyness or cunning, crafty subtlety, diplomacy
As well as,A plagiarist or a demagogue, in short, persons who are guilty of fraudulent representation or misrepresentation in speaking or writing
In short, Mercury/Pluto combinations seem to produce a persuasive bent in the manners of speaking, as well as the occasional mistep into dishonesty.Hasty thinking and speaking, premature action or hastiness, the spirit of opposition
In addition, and though this is purely theoretic, a tendency with aspects to Pluto is for the needs of the conjoining planet to operate in a mode of "all of mothing," and I this might possibly be the case with Mercury/Pluto combinations as well. Which is to say that the Mercury/Pluto might simply have a tendency toward talking way too much or not at all.
Thoughts on people with this aspect as well as on all I've given here are warmly welcome, let's start a discussion