I feel that the way text mesages are handled in iOS 16 has taken us a step backward. I am using Voiceover on an iPhone XR.
1. First the good. Nice that when one is in the Messages app in the list of messages, one of the context menu items (flicking up/down with one finger) is "mark as read" or "mark as unread". I've waited for this feature for a long time.
2. Unfortunately, when reading a mesage on the locked screen, there is no context menu item for "mark as read". Thus, after reading a text mesage on the locked screen, the only way to mark the message as "read" is to get into the Messages app itself, find the read mesage in the list of messages, and then finally mark it as "read" or open the message so that it will be marked as "read". too many steps. The problem is that if one can't easily mark a message "read", the Messages app on the home screen still notifies one that there are unread mesages even if all messages have been already read from the locked screen. Please add such a context menu item on the locked screen to "mark as read"!!!
3. In iOS 15, it used to be possible to have a message on the locked screen marked as "read" by activating the mesage and then hitting the "dismiss context menu" item. Now the mesage is marked as "read" and you don't see a reminder that you have unread mesages in the Messages app on the home screen. Anyway, this functionality seems to have been lost in iOS 16. See my item #2 above for a suggestion on how to rectify this.
3. A long standing issue with using Voiceover in the Messages app is that, when flicking through a list of messages, Voiceover announces the "unread" status of messages only after vocalizing all of the names of the recipient. Thus, if one has mesages in the list with many recipients it takes some time to flick through the list of mesages and figure out which of the messages in the list is the "unread" message that you want to read. My suggestion here is that Voiceover announce the "read/unread" status of mesages in the list prior to speaking any recipients or mesage contents when flicking through the list of messages. This would make it a lot more efficient to find "unread" messages in the list.
In designing UI's, one must not only think of "accessibility" (i.e., can one find and read all elements on the screen), but the designer must also think of how productive the interface is when used by a Voiceover user. Yes, the Messages app is "accessible", but it is not productive and efficient to use with Voiceover.