Mercury in Libra is pleasing. They are natural diplomats, or at least make the effort. They wish everyone were equal in the intellectual circles. It is very important for them to have a mental connection to those they have relationships with. Chances are, if they feel there is no connection, it is because Mercury in Libra is trying too hard to be intellectual in their relationships instead of paying attention. They have a need for fairness, but their constant comparisons can appear to be unfair instead.
While they strive for perfection and can't help criticizing, they try to be tactful. They are always looking for compromise, so everyone is happy. Opinions from either end of the spectrum can make them uncomfortable, but if they favor the middle ground, Libra Mercury is happy. This creates a great personality for a counselor or mediator. It may also cause them to be indecisive. They can't help but see both sides to everything. This may cause them to lose out on opportunities sometimes because they take too long.