The picture isn't real difinitive but it looks like the crack is in the nipple, not in the rim wall itself. Is this correct? Is the "nipple" I see in the picture a separate item or part of the rim?
The "nipple" you see is part of the rim. The original Shamals had recessed spoke nipples that required some fancy narrow socket tool to turn, and of course, I have one somewhere because I had the cheaper Ventos.
Superglue won't help. However, if you're really anxious to keep that rim, I wonder if a metal shop that does aluminum welding would be able to put in a spot of whatever to shore it up some.
You can simulate what would happen if it broke through by completely untensioning the spoke but that might cause other problems.
the nipple on this wheel normally resides inside the rim and has started to pull through, causing the outer rim wall to crack. eventually it will pull all the way through if the wheel continues to be ridden.