The main difference between company and sitting company is reflected in their meaning and usage. Company means to be a guest. Written language is common in some books. Sitting company tends to be colloquial, taking the literal meaning and sitting company, so we should pay attention to it when using it.
The two words "accompany" and "sit accompany" have the same pronunciation, only one word difference, but they are still different. They have different meanings in different scenes. Therefore, when writing some written language, you must not confuse them, otherwise the meanings will be very different.
The meaning of accompanying is very simple, that is, being a guest. The word is more written and often appears in some novels, such as the third and ninth times of a dream of Red Mansions. "The old lady said, she would also put a table for sister Shi to drink and ask us to accompany." This means being a guest.
Sitting with him is even simpler. It literally means sitting with him. It can be used for a scene where one person is lost and another person is sitting with him. For example, Xiao Hong doesn't know how to comfort him when he fails in the exam.