No more Mr. Nice Guy. If another aikidoka (senior or otherwise) tries to challenge my technique he/she better be up to the same challenge from me (shihan excepted, of course).
Earlier in this thread I asked why you would return a challenge from a 5th or 6th dan, but not from a shihan. I wasn't trying to ask a snide question (although, admittedly, I can be snide without trying). I remain curious.
Is the distinction really a distinction between the instructor and a fellow student? I can understand that (although a seminar instructor might be a 5th or 6th dan).
Or is the distinction about having greater respect for a shihan? Even though a shihan might be a 6th dan?
I guess that my curiosity is really about respect and etiquette, and how you -- and I and everyone else -- decide what lines to draw and where.