Messages in usual chats have only part of the width (of ‘messages’ part of the app window). Your messages aligned to the right, and others messages - to the left. It gives nise and clear distinction, and is something like ‘industry standart’.
But it has no sense in read-only channels, where you can’t write, and only can read.
More reasons for making messages in channels (almost) 100% width:
It’s a waste of screen space now.
Channel messages text content are often longer than chat contents, so they will benefit from full width.
It will give even clearer distinction between channels and chats, without breaking overall design patterns.
Expected behavior
Full message width in read-only channels.
Actual behavior
As in bi-directional chats, read-only channel messages have only part of available width.
Maybe it makes sense on some screen widths, but we might not want it if the window size is too big.
Although maybe window size being to big is anyway something that’s weird, IDK.