i believe that all information about compatibility changes should be kept for historical reasons. i find it always educational when i can see how a language (library, application, ...) evolved over time.
however anything not supported by a compatibility mode could be moved to a history section. this is helpful not only for old code, but also for old documentation. if i find some post explaining how to solve something in 7.4, then the history section can tell me how to fix that example to make it work in 8.0 the pike book for example just barely covers 7.6... greetings, martin.
