A simple thing Hey reminded me about. If you implement some sort of context actions (right-click menu, per-object floating panel, etc), those actions should be the same EVERYWHERE you see that object.
If you get this wrong, it creates confusion. People don’t think in terms of contexts, they think in terms of objects. If I see the same letter, looking the same, I don’t care what context I see it in. I expect it to do everything letter is supposed to do.
In case of Hey, if I see a letter in Screening context, I can preview it but can’t reply, in Read together I can’t neither sort nor reply, finally, when I am replying, I can’t sort it.
Other notorious example is macOS. In Windows, no matter where you see the file, you can do exactly the same things with it: open, rename, delete, etc. It works in Explorer, in Start menu, in File dialogs—everywhere! In macOS, it only works in a Finder window. If you right click on a file inside File dialog, you’ll see just four basic actions. If you put a file to Dock, you can only open it. Finally, if you have a folder shortcut and find a file there, there’s no context menu at all!