All writing as autobiography
There is a common quote that goes:
Great men discuss ideas; Average men discuss events; small minds discuss people.
Firstly, this quote is often misattributed to Socrates(which anyone who has read Plato's dialogues will find no mention of this anywhere) and to Eleanor Roosevelt(whom it's not the origin of, but probably popularised the phrase). It has an older origin with Charles Stewart's autobiography which recollects the following with him remarking on his friend Henry Thomas Buckle.
His thoughts and conversation were always on a high level, and I recollect a saying of his, which not only greatly impressed me at the time, but which I have ever since cherished as a test of the mental calibre of friends and acquaintances. Buckle said, in his dogmatic way: “Men and women range themselves into three classes or orders of intelligence; you can tell the lowest class by their habit of always talking about persons; the next by the fact that their habit is always to converse about things; the highest by their preference for the discussion of ideas.”
What is notable here is that it is only test of the calibre, and that they only prefer to talk about their respective class's element- however this should be tempered. Discussing the ideas of Socrates while removing Socrates himself, is in effect a diminishment of the ideas when compared to the people of Socrates time. The same can be said of the ideas of Jesus of Nazareth- taking the ideas and separating them from the man diminishes the idea itself. As for why, call it a lack of accountability to their idea- the idea being practiced is the proof of its sensibility. An idea lacking practice in its author, is proof of its ridiculousness(either of the author, or of the idea... or both!).
A good example of this, is people not wanting laws changed to outlaw things retroactively, yet wanting them to be punished retroactively. Another example of this is in wanting things to be done according to the law, but talking a lot of rubbish which prejudices the trial and prevents it being fair. These people have the idea of the law, and their own personalities betray it.
Another interesting example of this is in Nietzsche, who being sickly and ill, talked about the will to power- an elusive goal to him. This idea isn't unique though, Nietzsche picked up on it, and remarked about this with respect to Schopenhauer and with respect to Wagner(in the case of Wagner and in the increasingly Christian flavour of his Operas). This is even seen in the writing of early and late Nietzsche(Thus spoke Zarathustra and beyond good and evil having very distinct and strong tones, compared to the Birth of Tragedy which to me read a bit more academically, and with some anxiety).
What I wanted to draw attention to here, is just that ad hominem, isn't possible to remove from a work, as a work is in effect an autobiography of the person from their perspective and time in the work. That said, for some works(particularly artistic works), they are the person with the most time spent on that work thinking about it and how all the pieces fit together. To some degree this contrasts with the idea of "Death of the author", the general notion that a work should be taken without considering the author.
As marked before about the diminishment of the idea by the removal of the author, or the author diminishing their own idea(probably in some neurotic twist of fate). Quite often people unintentionally do this diminishment-- and a common way of doing this is to name the author insane(which is why a lot of systems rely on the plea to insanity in their court system, as a test of the author, as this plea, renders their works the workings of a madman).
What comes of this, is 2 snakes twisted in a Gordian Knot, as any writing of another's work is inevitably an autobiography of your reading and interpretation of their autobiography- and often going deeper as works are this reactionary hairball of witness testimony.
That said, I wouldn't want to pollute the word autobiography, as actual autobiographies exist to document a man's life and his events.
The work is the mirror of the soul.