I find the feature where channels with unread messages are in an UNREAD category that's above my FAVORITES to be very helpful and useful. I often have a few such channels at any one time, and I often read and answer them all at about the same time, switching between them.
The problem is that, as soon as I read through or respond to one channel, it is no longer UNREAD, and so leaves that topmost category. Often I want to respond with an additional line of text, or make an edit -- but now it's difficult to find that channel again!
Long story short, this suggestion is to not have those just-read channels disappear immediately from the UNREAD list, but to persist there (dimmed) for some (user-configured) period of time; 5 minutes, say.