"Enrolled in a course" is more formal than "signed up for" a course.

"Common photojournalistic practices tended at that time to isolate and victimise the person with AIDS." In other words, when there were articles about AIDS patients back then, the photos usually depicted the patients as frightening, freakish, or in some other way worthy of being ostracized. Personally, I wouldn't have used the word victimise here, but I understand the concept. The journalists were not being kind, because they depicted AIDS patients like lepers or worse. To answer your question, the journalists were being unkind to people with AIDS.

Well, I can't answer why, because there is no logic to it. But I can give you some examples. I am at my desk. I'm sitting in a chair. I am at my desk. I'm sitting on a chair. (Both are correct). My friend was sitting in his wheelchair when I arrived. (not on his wheelchair) I thought he would be in bed, because he had told me he was ill. I went to his bedroom first, and all I saw was his robe, which was on his bed. He was downstairs having breakfast on the balcony. (not in the balcony) Also, I'd like to add that a person sits: on a bench, on a stool, on a couch/sofa in bed (if under the blanket), on the bed (if not under the blanket), in the bathtub (if in the water), on the bathtub (if on the edge of the bathtub) in the bathroom, in an easy chair, at a desk, at a table on the toilet, on the floor, on the grass, on the tennis court, on the deck, on the roof in the garden, in the basement, in the attic, in the kitchen/office/living room, etc.

I arrived at the station thirty minutes early, so to kill time, I bought a magazine and sat down to do the puzzles in it.

You could sign up to run a race or sign up to volunteer at a fundraiser, but you only enroll in a course or enroll in school. The main difference is that enroll is more formal, and it can mean becoming a student, as opposed to choosing a particular activity or class.

You would use 'the next day' if this happened several days ago. But if she said it today, we would say tomorrow, because that is still tomorrow. Does that make sense? Here's another example: Last Thursday, my sister said she'd go to the post office to buy stamps for me the next day. I asked her about it today, and she admitted that she had forgotten to go. She said she'll go tomorrow. I hope she doesn't forget again!

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I can tell you it's not about our traditional use of the word engaged, meaning betrothed. In recent years, engagement has come to mean something similar to involvement or interest.