I actually reported this in a question way back when I first joined. It's partly why I was stuck with the name "ccornet" for so long back then (it was supposed to be ccomet), and it's also how I changed my name to "Grace Note" two days ago but can change it back as early as July 11th. It was established that this was basically a feature, at best it allows you to change your name once a week, and it wasn't worth fretting about for the effort it'd take to implement validation on the profile copying. So I deleted the question.
There was also a report, admittedly in just a comment, in this early post. It didn't really raise much steam, so I always assumed it was something of a silent trick.
The direct cause is that profile copying, not merely association, does not get validated for name changes. This is because it is just copying data from one table to another, instead of accessing the Name and changing it directly. So the copy function ends up bypassing the restriction. The name change in itself is expected behavior, but the bypass may well be.
The new system causes automatic profile copy in some scenarios when you associate two accounts. I haven't quite figured out what these scenarios are, as I've been repeatedly associating and unassociating my SU and SF accounts but neither had a profile copy that wasn't manually instigated by me.
status-bydesign
♥ ♥ ♥ ♥ ♥ ♥ ♥ ♥ ♥