Auto merge duplicates doing more harm than good

[Talisman]

When somebody posts a message, email notices are sent to those subscribed to that thread. Now, if that same poster goes back to edit that same message ten minutes later, all those people who received email notices won't find out that something was changed, added, or deleted unless they happen to re-read the same message again once they come back here to visit the site.

The flow of discussion in that thread could quite easily have continued on to another page by this time. Most folks don't scroll back far enough to re-read all the messages they're already familiar with, so they read on from the point in the conversation where they left off. The result of this being... that a good number of people don't find out later that the original content has changed.

If this has never been a problem when messages are edited on purpose, why is it such an issue now when subsequent posts have been automerged?