a similar distinction between Masochan use --- and Masochist use ---?

Didn't know that masochist was an eponym, Bingley. But I see that you're right. [Pls see * and Note below] This psychoanalyst - see below - observes that "masochism" is a term of "little precision" -- which makes sense, I suppose.

We all make mistakes and mistakes bring us pain. One could go around in circles endlessly wondering if those mistakes are 'wilful'.

On the other hand, causing pain to another is something which can be studied with scientific precision. One merely needs to establish that a person is inflicting pain on another person and the oppressor is aware of it and persists for no valid reason [i.e. no reason apart from the pleasure the pain brings to the oppressor].

Notes on Masochism: A Discussion of the History and Development of a Psychoanalytic Concept
William I. Grossman, M.D.

The term masochism, however, never did have a precise meaning or one that was generally accepted. It was a controversial term except as a literary designation for any phenomenon in which sexual pleasure and physical or mental pain were associated. The writings of Sacher-Masoch, which have been examined in an excellent literary and psychoanalytic study by Lenzer (1975), provided a prototype for all masochistic perversions. As Freud's concept of masochism evolved, the relation of partners in the masochistic perversion became the model for the relation between intrapsychic agencies, and masochism became a fundamental theoretical concept of drives and structure.
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At present, it has become evident that masochism is a term of little precision and that its value is descriptive and evocative.
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Part II presents one of a number of ways in which Freud took Krafft-Ebing's ideas about masochism and gave them a psychoanalytic shape.
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Reporting on the Kris Study Group's examination of the problems of definition and usage with respect to masochism, Nersessian (1983) noted the confusion that arises when a term is used to refer indiscriminately to perversion, behavior, character trait, and instinctual drive. He added an interesting observation: "Not only did we find that not everyone agreed that a particular behavior was masochistic, but also that … it was often very difficult to maintain that view once it was challenged" (p. 3). This observation suggests that multiple viewpoints are possible: from one perspective, behavior may be masochistic, and from another, not.

http://snipurl.com/g96a

* Leopold von Sacher-Masoch
(born, Lemberg, January 27, 1836 - died, Lindheim, March 9, 1895)

Sacher-Masoch is best known for the novel, “Venus in Furs,” about the masochistic relationship between Serverin von Kusiemski dreamer and dillatante, and Wanda von Dunajew, a beautiful, free-spirited widow, to whom he becomes a slave. The novel is based on real events from the author’s life. It is was also the novel that Dr. Richard von Krafft-Ebing singled out in the origin of the word “Masochism.”

http://snipurl.com/g97w

Note: If "masochism" is a condition lacking the indicia required to make it the subject of authoritative scientific investigation, then it follows that one cannot be a "masochan".