Alrighty, aMule did pass the night without a crash with ED2K enabled, all messages filtered, despite a few server connexion / disconnexion. So it might very well be that reconnecting to a server actually triggered a reconnexion to a client which was sending one of these automatic spam messages. For the record, my previous message filtering settings were to filter on 'HyperMule'.
I do hope all this will be helpful to the devs.
Cheers