I'd like the ability to remove or hide an link preview inside a channel.
The current settings let you turn off all previews across all chats. The poster can put <> around a link to suppress the preview. But the viewer has no way of closing or removing a preview after it has been added without turning off all other previews.
An initial change could be just be the option that hides the preview. The item being hidden wouldn't persist between page refreshes/program reloads.
A more full feature would be remembering what individual previews have been hidden/removed.
An awesome feature would be the ability to turn off previews on a per-channel or per-user basis.
But I'd be satisfied with the first change.