True story ! I know someone who does that all the damn time. At first, my innocent ass thought she goes out of her way to trade tickets to get in the front, but one day, we entered the venue around the same time and when the concert started she literally pushed her way to the front.
At first I thought owell, people are like that, no big deal. But they remember your face after you do that, especially if you're a regular. She's an old lady who likes to low-key stalk them and buy them expensive presents.
I'm not the type to be bothered by things like that, I would still talk with her.
But one time, while I was queuing with another group of friends, the topic of rude fans came in our conversation. And I remember them whispering to me how much they despise this lady for being so rude XD.
On a side note, one time I was pulled by a friend to go with her a little bit in the front (basically a little bit past the middle of the venue where I was sitting), and the venue had those bars that would divide the crowd. Nobody was too eager to go too much in the front, but I did feel a little exposed at that time XD (me being this tall blonde European with Japanese friends around XD).
I don't recommend being so adventurous because people in general can be mean, regardless of where you are :). But if you have luck and nobody sees you, we ain't gonna snitch on you ;).