I'm porting some of my code from P5, and it seems that MethodAnnouncements are no longer being fired on anonymous subclasses.
normalCls := Object subclass: #Something.
anonymousCls := normalCls newAnonymousSubclass.
normalCls removeSelector: #meNormal.
self logCr: ''.
methodAdded := [ :method | self log: method; log: ' '; logCr: method method printString ].
methodModified := [ :method | self log: method; log: ' '; logCr: method method printString ].
SystemAnnouncer uniqueInstance weak
when: MethodAdded send: #value: to: methodAdded;
when: MethodModified send: #value: to: methodModified.
anonymousCls compile: 'meAnn ^ ''add'''.
anonymousCls compile: 'meAnn ^ ''change'''.
normalCls compile: 'meNormal ^ ''add/change'''.
SystemAnnouncer uniqueInstance unsubscribe: methodAdded.
SystemAnnouncer uniqueInstance unsubscribe: methodModified.
a MethodAdded a subclass of Something>>#meAnn
a MethodModified a subclass of Something>>#meAnn
a MethodAdded Something>>#meNormal
a MethodModified Something>>#meNormal