Two suggestions here :
1.
The empty or black comment icons to indicate whether I have read, or not read, all posts in a thread are great.
But being right justified they weave left and right due to the different values to their right. No big deal but it kind of is!
The title of a thread and whether you have read everything within it, are the two main points of information about a thread.
The read/unread comment icon should be left justified - so the eye can whizz down titles and whether they are fully read or not - without janking left and right, left and right, left and right, left and right.
When left justified it would obviously be important that they are the first item to the left (of any other other icons/data if added), just so that they are all in a perfect vertical column through threads.
It would help enormously.
2 :
There could be a third state (as worked well at DPR).
Black, never visited before (all unread).
Half black half empty, visited before, new unread posts.
Empty, all posts read.
/
Oh and BTW as I mentioned before you really need to add the name of who started the thread on the left. And yes I’d prefer their name rather than an icon (same goes for the last poster on the right, their name rather than the rather ambiguous and so meaningless icons).
Many thanks!