I believe that comfort when using headphones depends to each person's head size/shape,ear size shape etc.
For example,I see too many comments about the "supreme" comfort of the Sony MDR 1R. I have the Sony's and I also own the shure srh840.It may sound strange,but I find the shures to be maybe a bit more comfortable for longer listening sessions.
My ears are 6.5 cm and I think they are normal shaped,and don't stick out that much.When I'm using the MDR 1R,although they are lighter and have less presure compared to shure 840,my ears touch a little in the inside covering of the drivers,causing some iritation at longer listening time.It's not bad,and I feel it after I put them off my head,but it's there...
With the shure 840,I don't have this problem.
Also,I find the shures a bit more comfortable compared to my koss portapro,because portapro also causes a bit of pain the way they touch my ears after some listening time.Again it's not that bad and i feel it after I finsh listening and put them off.But it's something I don't feel with the shures.
Same goes to the AKG K550 (which I had for few days)vs SHURE 840.Although the k550 seemed more comfortable at first,at the end it was worst for me,because at the position I had the proper seal and sound,the headband pressed my head on top and it was a bit annoying (although not much).I also had the problem with my ears touching the hard plastic covering of the drivers,causing me a bit pain after some listening time.This iritation was a bit worst compared to the sony mdr 1R,and it was one of the reasons I returned them and kept the 1R,although I liked their sound better.
So,I had this experience with these 4 headphones,which is a good example,that although at first a headphone seems the most uncomfortable (shure 840),it ended up to be the most comfortable of the others for longer listening.
If I was at a headphone meeting and was asked to try these 4 headphones,and tell which is most uncomfortable,I'm almost 100% sure I would pick the 840,but living with these headphone for some time,I came to the conclusion that the shures are the most comfortable FOR ME.
So maybe we should not judge the comfort of some headphones compared to other models if we only try them for a short time at a shop or at a meeting etc.