The .topic-owner class exists within threads, so something could be done to that class in style sheets for posts inside threads in the meantime…
Glancing over the Discourse GitHub, it looks like the best way to implement this would be to add another tracking option to their topic-tracking-state.js.e6 code. Problem is, I’m not super certain how you’d ultimately go about properly getting the details for each unread post quickly in the tracked threads so that they can be compared to the topic’s owner. It’ll probably come to me if I get to spend more time on this, I guess, but I have to go shower and help my mother carry some paintings in a little while.
If I come up with something I’ll fork the current master and submit a pull request.
Edit: I’m back and I’m testing the waters a little by proposing the addition of a ‘Show tracked posts’ link in the User preferences window as I try to figure out the best way to implement stuff. But from a casual glance, it looks like tagging individual posts is currently not a part of Discourse’s tagging system (which was originally a plug-in that’s been, shall we say, ‘grandsonned’ into the core). While implementing would be relatively trivial, chances are that it might also be kind-of catastrophic because the way tagging limits access is via trust levels as opposed to, say, topic ownership.
On the other hand, if the LP Zone were to have mega-thread like topics, being able to have multiple people use the “update” tag on their individual posts would probably be the only way to track non-topic owner updates. Same if we ever have LPs that are abandoned and then continued or finished by another user, though for the Zone’s purposes it would probably be better to just transfer topic/post ownership to said different user for the sake of editing the first post…
Anyway, what I’m saying is that even at the conceptual stage I’m not super certain I can implement anything other than a band-aid for our problem without overhauling more of Discourse’s current core than I feel their devs will be comfortable with (since it seems like a sort-of niche feature request to add both Topic Owner Post Tracking and Individual Post Tagging).
I’m not saying I won’t try- I’m just saying whatever I make might end up being a Discourse plugin instead.