However, I noticed that there is now a maximum displayable window width for the forum pages, and if you try and expand the window wider, it just stays the same width, centered, with blank sides. So, if the original size of the hotlinked/embedded "img" image is beyond the maximum displayable width for the posting area (as in the link above), then you can only view the scaled down size on the forum page, unless you view the image separately (for example using "View Image" in the popup menu in Firefox).
Another new thing I noticed is that when the width of the window is reduced below a certain point, the member info suddenly moves from the left side of their posting to the top of their posting, which likely helps with the viewability for those using mobile devices.