Writing between the lines shows that the writer needs lot of social recognition. These people live to be the center of attraction.
They will keep doing something which gains appreciation. Sometimes they unknowingly do something which gains attention in a wrong way too. Getting trolled, being accused, being envied, getting blamed or anything is fine for them as long as there is a chance of being the center of attention.
Theory of Graphology: writing on a ruled paper is like working in an environment of fixed set of rules. The person writing between the lines does not want to be bound by rules at the same time does not want to disobey. Such a person will be innovative and maverick. Seeking attention, recognition and appreciation is what they do.
