I just don't think it should be a "responsibility" of mine. If I know it is a new player or someone's first challenge, or even first few, I will automatically be more cued in because they may be more confused over challenge protocol. I would automatically be offering suggestions and assistance. For a seasoned player, however, I would be concerned that they are going to take that as nagging...but I also know they know how to challenge correctly.
I do understand what you are saying and I think it falls back on what G was talking about last night in regards to the community self policing. I realize that was in regards to barons and titles but it should extend to other things as well.
Speaking in broad terms here, and not intending to personalize this, I do think, ultimately, the whole process being followed with as little unintended fireworks is very much the responsibility of leadership.
It's just a matter of whether you want your (any of you supes/assist. supes) responsibility to kick in before (and keep things on track) or after (after things have already headed downhill).
Since leadership has to make sure the rules are followed, wouldn't it be easier/friendlier/more useful to make sure ahead of time that all the steps were completed, rather than taking punitive action after the fact? I get that we all have other things to do than camp the message boards, but if the challenge falls apart, someone is going to have to deal with it sooner or later, right?
I guess I think the time for "heavy handedness" comes before the match rather than after/at the time of the match. I say that coming from an admin/captaining standpoint! I want to know beforehand if things are on track, not be hit with a surprise the next day or at 11 pm just as I'm ready for sleep.
And after saying all of that, I don't like this rule in the first place. I don't think the responsibility for finding a caller falls only to one side. I think it's a discussion for the two to agree upon, just as they have to agree upon a date and time. I would NOT agree to one person unilaterally picking the caller. It's nice if they make the offer or make suggestions, but this is something that should be negotiated ahead of time.
So... I fall on the side of this doesn't need to be a rule, but that someone should make sure all the steps are followed--and yes, I think that should ultimately be a supervisor/assistant supervisor if no one else steps up to mention it. A question from another dueler, an offer to call from a volunteer, a caller posting they've agreed to call, or one of the bosses posting "who's calling?"
Bottom line: keeping the communication open starts at the top,as it sets the example for the rest of us.
And to reiterate, this is no way me saying "Gabby is responsible for all the things." No! But if things fall apart, somewhere a line of communication was broken, either by someone not knowing the steps, someone deliberately being difficult to deal with, or someone not noticing that things are not very clear, and then taking the steps to clear up any confusion. Putting this particular issue all on the back of the challenger I think is the wrong way to look at it.
Anyway, I spent more time on this than I meant to.

Thanks for listening!