Could the soot on the spark plug base rings be oil residue?
My plugs have that too, and the insulator and electrodes look nearly as good as yours.
Last check I'm adding oil more often than I like, which may indicate the source of the base-ring carbon on my plugs. I have about 20K miles on this set of OEM Kaw rings installed in 2015.
I usually ride in the upper safe RPM range, which in my mind may account for additional piston ring wear if compared to a similar engine run consistently at lower engine revs.
Installed new Viton valve seals in 2015, but I wonder if they may not work as effectively since the cams were changed from standard to ZX at that time, but the 8K mile original valves were just checked and reused.
I guess it could be but I'm thinking more it's rich up to 3/4000 RPM's. My rings were reused so I suspect they are leaking as well as I know the Viton seals are leaking. I got oil on my finger tip when I had the intake boots off. Not long ago the bases were cleaning up so that's where I'm trying to go by weaning it out little by little.