Sorry, I don't think it's that easy to miss the fact that there is a special event going on & the park is closed. Disney has the park hours listed online & it clearly states 7-12 as special party hours. I don't believe someone spends $100 a person to get into a theme park without checking the park hours. If they do, that's really poor judgement on their part. Plus there are signs outside at the TTC & at the MK gates that state the park is closing at 7 for a holiday party.
Oh I totally agree with you (as I stated I research) about that except for the fact that there are people who still do little or no research when it comes to WDW plus people are just not observant at all which yes is poor judgement. Some people also may not know the language well enough to read the signs.
I was just placing my input based on bad reviews (which I didn't always feel was justified since a lot was because the reviewer didn't research) I had seen based on the parties over several months time where people clearly didn't realize they were there on a party night and therefore must not have been observant enough to see the signs you were talking about or looked at park hours. If not approached by a CM telling them to leave some of the people below may not have realized what was going on and carried on like normal. As I also mentioned I was more speaking of Halloween though the same logic could be applied towards the Christmas party.
Just some MK reviews from TripAdvisor:
1-star review from 11/7/15: "Unfortunately we went in the week of Halloween. We did not get to see any disney characters as they seemed to save them all for the Halloween evening entertainment. The park closed at 5pm and we were told that we would have to pay extra to stay. If we had know we would not have paid to go into the park at all. Everyone was very disappointed."
1-star review from 10/24/15: "They wouldn't even let us in because we didn't have "event" tickets and you can not ride some rides without a costume that's not right."
2-star review from 9/25/15: "How dare they charge you for a full days ticket price and boot you out at 7pm for the Halloween event"
2-star review from 10/19/15: "...about eight minutes before the park "closed" for the Halloween party for which we didn't have tickets. She would not let us board one final ride we wanted to check out before we left for the night."
Just some Universal reviews from TripAdvisor:
2-star review from 12/14/15 : "...they are more worried about making money than making guests feel welcome, the tone is visible everywhere but you will feel it most intensely when they ask you to leave the park early due to the "Horror Nights" which in my point of view should not be in detriment of average ticket paying guests who had the bad luck to go on one of these days and had to deal with rude staff demanding everyone to leave."
2-star review from 10/9/15: "We visited Universal Studios on a Thursday. We arrived at noon and it wasn't until 5pm that day that we were told that it closed at 5pm (the website had said 10pm) because of a Halloween event."
These are from people who actually posted reviews but there are plenty of people who don't post reviews. I was in no way defending those who are at the parties unknowningly (as I am not taking into consideration people who knew but stayed anyways) without purchasing the special event tickets but it does happen.
We could argue all day long that these people should have researched or observed signs in front of them but the point is they didn't and they felt the need to rate low based on that (though some of the reviews it was a combination of multiple things that led to a low review).