Every now and then there are posts which either are deleted or changed after replies were made.

I think there are rare occasions where this make sense, but generally it is a bad habit.

Deleted posts which have a chain of replies can really mess up a thread, since the replies are to - what?

A similar thing are posts which are edited and filled with different content after replies were made, instead of starting a new thread.

This leads to thread inconsistencies, and this happened several times recently, so following those threads can be unnecessarily difficult.

Ray

This feature was already abused in the past (anybody remembers Don W. ?). I concur: it's a bad habit.