I have “hide read posts” enabled on Lemmy. Unfortunately it does not show any of my saved/bookmarked posts because of this
I just noticed the same issue on seeing your own posts. Other apps like Mlem, Memmy and Voyager seem to have found a fix for this, because in those apps I can both see my saved posts as well as my own posts, even though I’ve already read them.
I like this idea, but it should also bookmark any post you reply to or create. 
On. Larger note about hidden read posts. I feel there should be something to let us know that there would have been a post but it’s hidden because already read. Maybe read posts should be collapsed like comments instead of hidden.
Do comments make read posts reappear as unread? It seems to me that post that have activity should reappear based on some preference. 
And continuing my feedback on this topic, I also think you need to be able to customize per feed if you want to hide or not hide read posts