I have seen this problem posted before by others and I have also posted it but there has been no fix. I thought maybe I would get used to it but no, it is still a royal pain. I read my email on the web. I leave/mark many messages unread if I have followup to take care of. The upgrade caused issues with this. Just touching an email marks it as read and it drops out of sight the next time the server is pinged. Sometimes new emails get "touched" and drop out of sight before I even knew they were there and I miss something important. Sometimes, when trying to read an email, it just disappears. I can find it again in my read mail but that is a nuisance. Please, Comcast, return the functionality that worked for me.
They actually disappear while being read!
It is a function of having my email sorted by unread. Once I "touch" it to read it, it is marked unread. Then as soon as my email pings the server again, the read emails drop out of the unread section into the read section AND does while I am in the middle of reading it, even scrolling on it. It is very frustrating. I can find it but I shouldn't have to.