hmm, a non programmers answer
a post is an entry in a database
postid|subject|body|author|parent|
I would add
postid|subject|body|author|parent|uidMarkedReadHash
where uidMarkedReadHash is a hashed key to the userbase with a bit toggle for mark read
a few random thoughts,
Bill
Any opinions expressed by me are mine alone, posted from my home computer, on my own time as a free american and do not reflect the opinions of any person or company that I have had professional relations with in the past 50 years. meep