Mercury in Cancer:
These people communicate with feeling, conveying a sensitive, withdrawn, and thoughtful nature to the people they interact with. If this is the only personal planet in Cancer in their chart, they may come across as more personal and sensitive than they actually are.
No matter how free-spirited the rest of their natal charts may be, Mercury in Cancer people can be very subjective and personal, or they opt not to talk at all. They are slow to respond at times, giving others the impression that they are deep thinkers. They probably are just that. Cancer is a meditative and reflective sign. Still, Mercury in Cancer people are much faster at forming opinions and making decisions than they appear. Because they listen so well to others, this speed is not obvious.
You can bet that Mercury in Cancer natives will remember almost anything — from their own past, to your conversation two months ago. You might notice their memory is a little skewed in the direction of emotion. The truth is, these people remember the mood surrounding all the moments they have stored in their memory. This is because they “feel you out” when you are talking to them. The words are not as important to them as the emotions behind them.
Cancer communicators come across as gentle, intuitive, and sentimental. Sometimes, they can appear quite defensive, as they can take things quite personally. They make you feel very warm and protected. Sometimes it is in their voice (solid yet soothing); and often it is in the message they are giving. Sometimes Cancer communicators can come across as if they are hiding something, which can get them into more trouble than they perhaps deserve.
Mercury in Cancer retains a lot of information, and learns best when they feel emotionally balanced. They prefer to focus their concentration on subjects, and approach problems in a step-by-step manner, “feeling out” an answer. This position gives the gift of rhythm and beat.
No matter what their Sun sign (and it can only be Gemini, Cancer, or Leo), Cancer communicators seem to have feelers. They pick up people’s emotions in conversations. They are the best listeners of all the signs. In fact, it is extraordinarily easy for them to get “lost” in the other person’s expression and opinion. For a while, they can almost lose their own opinions and completely step into the other’s shoes.
You can count on Mercury in Cancer to come up with information, culled from their outstanding memory that others have long forgotten.
Cancer communicators’ style is to avoid arguments. But, make no mistake about it, they can provoke arguments easily. They do this in a subtle manner, and then get hurt when others argue with them.
Mercury in Cancer is generally attracted to poetry, archaic language, expressions of yesteryear, and the like. Because they are so aware of others’ emotions, they can be somewhat diplomatic in their dealings with people.
These people appear to take their time when they make a decision, and even when they form an opinion. They need to step away from others, and be alone with themselves to explore all that they have absorbed. They ask for time to stew over new information. They are impressionable, and the smart ones know it. Withdrawing into themselves helps them to discriminate.
These people can get frustrated with facts-only thinking processes. They also dislike distractions when they are talking or thinking. They need to focus on the matter at hand in order to come up with the best solutions to problems.
Mercury in Cancer can be very effective speakers and writers, especially if they have Leo or Gemini Suns. Their ability to “feel out” their audience is extraordinary. Also, they are able to present things concisely, yet powerfully.
If your Mercury is in Aries or Libra, you may find some of your conversations with Mercury in Cancer natives are frustrating. (The feeling is mutual, by the way). Aries communicators get impatient with Cancer’s slowness and indirect communication, while Libra communicators wonder why Cancer always seems to personalize what they say to the point of appearing like they have funnel vision. This latter is not always the case — Cancer communicators simply prefer to speak about the matter at hand, you and them, and not the rest of the world as Libra tends to do. Likewise, Mercury in Cancer can find Aries communicators rather brusque, and Libra communicators maddeningly detached or other-oriented. (Source).