TLDR: My idea is to have a way for early edits (whole new chunks of text) to be highlighted while the post is still fairly new, so that the "EDIT:" convention is unneeded, resulting in less noise in the long run.
During the earliest stage of the life of a question, there's a convention to mark updates on both the question and answers with an EDIT heading. For example:
EDIT: More text
This is an effective tool to bring attention to changes in a post during that early refinement stage. But later, and for the rest of the post's life, those EDIT headings are basically noise. There are exceptions, but I believe that most posts (especially answers) can be made more reader-friendly by removing these headings.
So my idea, which I realize may be far-fetched, is to have a way for edits of this kind (contiguous blocks of added text) to be dynamically highlighted by the browser, making the EDIT headings unnecessary.
It could be just a change in the background color of the most recently added block of text, or perhaps something more elaborate that can indicate each added block in a progressively-more-recent fashion. Vertical (maybe squiggly) lines in the left margin may be another possiblity, though I don't know if that would require a whole new kind of control to be used (you can tell I'm not a web developer).
There could be a new markup tag to indicate text which needs to be highlighted in this way. This gives the author control over whether the edit is highlighted. So for example:
Here's my orignal answer. Here's my orignal answer. Here's my orignal answer. <edit>Here's some more detail I added a bit later in response to comments. Here's some more detail I added a bit later in response to comments. Here's some more detail I added a bit later in response to comments.</edit>
might show up like this (please forgive my freehand attempt at squiggly lines):
When the post moves out of its active phase, the dynamic highlighting could cease, leaving a neater looking post.
Does this make sense to anyone else, or am I on the crack?
One possible problem is that some posts may eventually seem to contradict themselves when the highlighting ceases to show. (Ideally, any post which does contradict itself should really be edited one last time to remove any confusion added by the earlier edits... but sadly this often doesn't happen).