When you press the headphones up against your ear you do a couple things, first is that you do tighten the seal, second, if you cup over any holes, you can also adjust airflow in and out of the housings (and the drivers), third, you adjust the distance of the drivers from your ears... All of those will change the sound a lot :p
EQing won't hurt the headphones, depending on who you ask, it can hurt the sound file that is being adjusted in real time.
Thanks for the info. So far digging the headphones. I have to say though I miss the bass a bit, but like I said I'm a bit of a basehead and I do have the EQ set to bass boost. Going to try without it this week to/from commute to work. I guess just like any other thing, you get used to it.