After playing around with “preferences” it seems the issue is with Chrome.
Using Opera in wide mode the scroll bar is correctly placed but in Chrome it is over the reply button.
In Chrome;
I turned wide mode off and view reverted correctly (normal) when browsing a thread, reactivating “Wide Mode” the reply button is again under the scroll bar.
It seems to me the width is not scaling correctly as the scroll bar is in exactly the same position as it is with “wide mode” disabled.