Before, when hitting the preview button you always could see how the post would look like.

Not any more, takes away all side bars and only show you text. (+formatting)

You mean with the preview showing the line breaks where they will be after making the post? I believe it has been the way it is now for a long time and unfortunately cannot remember how it was earlier but I do think that it was somewhat different. I don't see the current preview mode with the text taking up the entire screen width a problem, really. Attachments are still being shown.

--

Maestro

Before, when hitting the preview button you always could see how the post would look like.

Not any more, takes away all side bars and only show you text. (+formatting)

The preview was never exactly the same as the final post - it was always wider because there was no user name, avatar, etc to the left, so you couldn't be 100% sure where long lines would wrap and how it would look.

I can't see what has changed recently, though. Looks the same to me.