I am by no means an expert, but I am a member here and thus will throw in my opinions. :D
After reading this entire post there are clearly a few definitions of "fin", be it the markings on the edge, a "Y" shape on the edge, or just a term used to describe the very edge of the blade regardless of its shape. With so many definition I am willing to bet that a general consensus will never be reached.
Personally I don't think there is a "Y" shape at the edge, I just don't see how given the way we hone that is possible. There is certainly the possibility of honing too much and having the edge break down but that's still not a "Y" shape, just a extremely acute "V" shape that is falling apart and the very edge.
Now whether or not stropping and honing has a great affect on the physical properties of the steel at the very edge I have no clue, perhaps one of the 'smiths here can chime in.
I do feel that stropping has an abrasive quality. Clearly not so much so as to dis-color the strop but we can see from some of the pictures that get thrown around that the strop can smooth the grooves. I think this is what is happening when you strop. Not some aligning of a "fin" but a removal or oxidation. Now I know some of you will say "yeah, but I oil my blade and stropping still does something." True, but can you actually say that when you dried it you removed 100% or the water? I mean water molecules are pretty damn small and I'm sure that no matter how well you dried the blade there is still going to be some moisture left at a microscopic level that will cause an amount of microscopic oxidation and it is this oxidation that the strop is removing.
Hey these are just some thoughts. I love this place for its great discussions. I look forward to seeing some arguments as to why I'm wrong but be forewarned, there is an evil smiley with a shield and a mace waiting for you. :mace: