Most airline check-in counter staff will only see information about the traveller on that flight, and their frequent flyer details. As their main priority is to check-in travellers as quickly as possible, they'll usually just have the details relevant to your flight.
They may be able to look at your travel history via your frequent flyer membership with more time, but most check-in systems won't look at your history by passport number/etc. For that, you'd probably want to go over to the airline customer service/information counters first.
Most airlines only give special consideration for special requests if given advance notice, and those customer service agents would most likely look up your previous history and traveller details from your frequent flyer and past-traveller records.
Regarding seating, most airlines now pre-assign a seat (even if you don't know that) when you complete your booking, so that they can distribute the seating evenly. Pre-flight seat requests are generally not guaranteed, even if you pay for them, so it may have just been a pre-assignment that got you your window seat.
The only exception to this that I know of is if a customer has previously been blacklisted due to something serious (e.g. being denied boarding)