Why is 本人 inappropriate in an objective text?

Question

I know that in everyday life I should use 我。But I was under the impression that, when I am writing an impersonal text with some distance from the reader it was okay to use 本人。Below I wrote a text on why the 29th of May is considered unlucky in Greek superstition. I guess this kind of seriously unlucky, ominous day does not fit the definition of 倒霉。 But I don’t understand why my teacher marked 本人, 吾國 and (on other pages) 該日 as wrong.

Edit: if my language capacity was high enough, would the topic be appropriate for expressions like 本人，該日，吾國？ The topic is the sack of the city of Constantinople , as well as the behaviour of some good and bad rulers of the Ottoman Empire toward the Greek people. This is a very sensitive topic and in my native languages I would use most formal language, so as to keep myself to some objectivity.

Answer 1

本人 means 我, I in the formal circumstances, which is used to make a serious statement/declaration, such as in an allegation. For example, 本人郑重声明: 此事与本人没有任何关系！If you use this sense of 本人 in non formal settings, that would sound either pretentious or a bit joking. For example, 本人今天要去买东西 sounds pretentiously funny because 买东西 is really a very casual thing and people don't expect you to mess it up with such a formal word 本人, which add some taste of funny.

In casual speech, 本人 means in person, oneself. See these examples:

这照片是你本人吗？// are you the very person who is in the picture? Or is the person in the picture yourself?

你是Ludi本人吗？// are you Ludi himself?

你本人能(亲自)来吗？// could you come in person?

吾國 and 該日 are old fashioned and we don't usually use these words in modern Chinese, especially within the mainland China.

Answer 2

The word 本人 stresses that it is you but not others. "本人" is acceptable to native speakers in this sentence, but it is mostly used in certain formal situations (for example, a plea of guilty). And it can indicate that you slightly look down on your readers when used in normal situations.
In general, 我 is the best choice for the general reference to oneself.

吾國 is understandable but it is not used since 我 is the preferred word to indicate oneself in Mandarin nowadays (but you can find the presence of 吾 in some dialects).

The word 该日 would lead to serious problem. 日 can be used as the f-word (therefore a verb) and 该 would be interpreted as "should" under this circumstance. Therefore please always use 这一天/这天 or other common expressions for this day.

And it seems that you like to use classical Chinese words （乃、吾） in your writings. It is better not to use then alongside modern expressions.