You're correct. On older trains it damages the door mechanisms. Silver set doors open very slowly because people force them. This causes the same self-important pushy tosspots to attempt to force the doors open at their station. Tangara doors can have their "rubber bands" stretched or even broken, which puts that set of doors out of action until they're repaired. Anyone forcing doors obviously has an immense sense of contempt for the rest of the passengers on the train, and should consider picking up a FREE timetable booklet so as to not have to run for trains and force doors. I've seen cars locked off because one person has damaged a set of doors. I'm sure all the people standing in the other cars were glad they made their train by forcing the doors.
There's a video by previous member, boxythingy, which shows the doors being sloppy and not fully opening, resulting in passengers having to actually the push them open themselves.
Here's the video
http://m.youtube.com/watch?v=sqwhKAIjlDg
Is this also a result of the doors mechanisms failing due to people holding the doors open?