Re: Use of the term Aikido"ka"
FWIW, my original teacher (who was Japanese) corrected us when we used the term. Inaba Sensei thought it sounded inappropriate unless the person was doing aikido as their primary, dedicated activity and was accomplished. He said you wouldn't normally use it for someone that had another full-time job, for example.
I'm sure there are shades of grey on this (language usage being what it is), but I've always shied away from the term since he explained it to me that way. Having said that, I certainly wouldn't get offended by somebody else using it, as it seems pretty common these days.
Remember the 80's video game "karateka"? Whenever I hear "aikidoka" I think "somebody needs to make that game!".