Diversity:
I have never met a more diverse group of people. I've met people who are from countries I had never even heard of, belong to religious groups I didn't know existed, have strange, and have the most obscure hobbies (e.g. champion bird watchers, world champion DJ, New York Times Crossword Puzzle Developer).
Out of Place:
Someone who isn't passionate about the world, and doing something important in it. Other than that, Harvard is a pretty accepting place.
What people wear:
There are people who wear everything. Most commonly, though, is probably just the basic t-shirt and jeans with sneakers or rain/snow boots. During midterms and finals usually sweats.
Different types of students interact:
Everyone can comfortably interact here. I have never felt like there was any sort of "group" I couldn't talk to. One of the nice things about Harvard is we all live in randomized housing so people can't self select to live in dorms with people who are only athletes or only drama kids, or only musical. Everyone is mixed in together, and find a way to get along.
Dining Hall Tables:
-Students who are studying quietly
-Students who are having dinner with their team
-Students who are sitting with resident tutors and getting advice about graduate school and career options
-Students sitting and talking and chilling with their friends.
Our tables are different because of what people are doing, not because of who they are. One student can fit into all of these categories on different days.
Financial backgrounds:
The vast majority of Harvard students are on financial aid. Many of my friends have full rides based on their financial situations. Many students are upper-middle class and a few are from very well-off backgrounds. This place is diverse, and every year it is getting more so. The Harvard Financial Aid Office, though, does a great job, and it is not obvious who is on financial aid and who is not unless someone tells you because they don't force students to work a ridiculously long amount of hours or take out huge loans.
Political Involvement:
There is tons of political activism here on both sides of the political spectrum. We get a vast array of top politicians on campus, and the events are always packed. During campaign seasons, hundreds of students spend their weekends in DC, New Hampshire, RI, and PA canvassing.
Earnings: No! Some people might say they would like to be better off than their parents or that they could live on nothing if they had too, but it would be considered in bad taste here to arrogantly brag about how much you might one day earn.