Here are the rule 40 guidelines: http://www.teamusa.org/~/media/TeamUSA/Documents/Rule-40-Guidelines-ENG.pdf?la=en
I don't see where athletes can't acknowledge their sponsors. It says sponsors can't use their athletes images, but what is to stop an athlete from doing it on their own. Clearly LetsRun.com as a journalistic entity can say Emma Coburn of New Balance so what's to stop Emma from acknowledging them?
I just don't see it in my reading of it.
On a separate note, the athletes need to just collectively ignore rule 40. The Olympics can have the same restrictions that the Super Bowl, the Ryder Cup, etc have. They don't need extra protections. What is the IOC going to do if every athlete acts like athletes in other sports and ignores the rule.