Great illustrations and your writing style uses a nice relaxed tone.
I had a set of those Italian switch blades confiscated at the border when I emigrated to the USA at the tender age of 14! I bought them via mail order and didn't know they were verboten. When we crossed the border with our luggage someone asked me if I had anything other than clothing in my luggage. I innocently volunteered that I had some knives. They were very nice about it, but that was the last I saw of my knives.
There are a couple different versions of double-locking mechanisms. The CRKT has a couple called LAWKS (Lake and Walker Knife Safety) and LBS (Lock Back Safety), Gerber has one called the Rotolock, and Lionsteel has one called the Rotoblock. They're supposed to provide an extra bit of security against lock failure, especially with liner locks. The problem is that any force great enough to cause a liner lock to fail will often break those secondary locks as well, or break the knife in such as way as to make the secondary lock useless (such as the pivot failing rather than the liner disengaging). Mostly a marketing thing.
Put it this way - if you expect to put a great enough to force on a liner lock where you think you'll need a secondary safety, it's much better just get a knife with a stronger lock, like a frame lock or back lock.
Edit: Just remembered, SanRenMu actually has a secondary lock on a couple of their knives as well.
That's the clearest and most concise overview of knife steels I've seen. Thank you for boiling it down to the essentials and providing such a nice foundation for further reading. I think I'll be referring to it again and again.
Sorry, updated the article to better explain the differences. G10 and FRN are essentially the same thing, it's just that G10 is an FRN handle that's been cut in to extremely thin layers and laminated back together. Micarta is only made with full sheets of material, while Pakkawood is only made with sawdust (loose material).