...a post highlighted itself somehow (an asterisk or similar) to indicate...
I would suggest to tag an updated node using CSS class attribute (i.e. updated) with a sensible site-default:
<div class="$AS_BEFORE updated">
...
</div>
Now, every monk can fine-tune the layout using own CSS redefinitions (
Help for Display Settings).
Something like i.e.
.updated { border-left: 1px solid red; }
or
.updated::before { content: "UPDATED: "; }
Perhaps add
ud-$YYYYMMDD or
updated-today or similar for more customisation options?