It happens when you can have a surprisingly easy and free dialog with a person you don't know at all. Already the first lines of dialog and here... You allow yourself bold jokes, comparisons. And after an hour of idle chatter direct text designates a person, drawing a conclusion from actions and words when it comes to life. Such conversations are very tasty, when you don't worry... what is there, you don't even think that you may be misunderstood or not understood at all. Tough answers to tough questions in both directions... Such conversations bring you closer, open and warm you up.
Keep it simple. Be yourself. Smiles and frowning eyebrows are very visible in the letters you read. The only thing that matters is that the person writing these letters is a Person.