This is quite common and pretty harmless. The scratches you see don't go very deep, nor are they very wide. My All-Clad saute pan is nearing 10 years old and has a ton of micro-scratches on the interior. It still performs beautifully.
That said, the scratches can grab onto proteins and cause sticking. However, this is simple to prevent with both oil and proper pan preheating.
When a pan is preheated properly the metal expands, essentially closing all of the micro-scratches. This prevents the proteins from grabbing onto them and getting stuck. You obviously need oil/fat to assist with this as well.
To properly heat a pan to the appropriate temperature I suggest using the water drop method. If you put a cold pan on heat and drip a drop of water onto it, the water will sit there for several seconds then boil away. As the pan gets warmer this will happen more quickly, fizzling away in a second or so. Once the scratches start to close something weird happens.
First, the drop of water will break into a few mini drops which scoot around the pan as they evaporate. This is a sign that you are almost there. When the drop of water stays whole (mostly) and scoots around the pan like a mercury ball, this is the perfect temperature. I the water instantly vaporizes on contact, you've gone way too far and need to let the pan cool down. At this point you should add your oil/fat, swirl it around, and immediately add your food. (Make sure the mercury ball of water is gone before adding oil).
Also note that the mercury-ball phase is definitely too hot for unclarified butter, and may be too hot for some extra-virgin olive oils. They may instantly smoke upon adding.
Again, it's important to have your oil and ingredients in place (mise en place) before you start. It's quite easy to skyrocket past the mercury-ball phase if you have to open your oil, pour, and then season your ingredients.
Heat the stainless steal pan on medium-high.
After its hot add your oil.
You'll know your pan is hot enough when the oil has wavy movment when you tilt your pan.
Now raise the temperature gradually until the oil begins become only slighty darker.
If you've reached smoke point you are done (the pan should only be SLIGHTLY smoking)
Remove any excess oil and add new oil.
Cook.
Small amounts of oil are needed for fish without the skin. But if the skin is on and your trying to get it crispy all of the skin on the surface of the fish must be submerged in water to get an effective crust.
Best Answer
It is not something that I would do - I just use stainless with sufficient oil. But if you really want to try it, then yes, you can make it stick. It is more difficult than with cast iron, but it is not impossible. First, steel does have "pores" (actually crags) on a microscopic level. It is not that much smoother than forged iron, which is also seasoned. Second, we have had enough questions around here of people complaining about "ruining" their stainless when they accidentally polymerized oil onto it. Third, my pans also hold a bit of polymerization on the walls, where splatter meets the hot metal.
I cannot give you the exact conditions under which it will work, but I don't think there is much difference between the best process for seasoning stainless steel and the best process for seasoning iron. The difference is in that you have a much smaller margin for error. But with good technique and patience, you should be able to do it on purpose.