That's a pretty fair alternative with the advantage that the update entry can be placed anywhere within the node text.

Just to clarify my own notion:

The text from the update field would be wrapped up and appended to the end of the node text thus (borrowing from your timestamp idea):

<update 2005-09-15 16:44>Let me clarify: I have a more specific notion
+.</update>
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and would render in a similar fashion to your suggestion:

<div class='update'><div class='updatehead'><b>Update</b></div>
<div class='update-date'>&nbsp;(2005-09-15 16:44)</div>:&nbsp;Let me c
+larify: I have a more specific notion.
</div>
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