The implementation of Browse Implementors in a method source pane has an off by one error.
I typed the source for a method and before I saved it, I wanted to find out whether it should have been a class method or an instance method. So I highlighted a message send and browsed its implementors.
The source was:
^super extraAttributes, #()
I highlighted the portion bolded (the super send).
The window that opened showed me implementors of #, instead.
If I highlight everything except the last letter (extraAttribute), the Browse Implementors does show me the implementors of #extraAttributes (with the "s").