When I tried to add an image to a post that was too large, I got this message:
I noticed that this was larger than the max width of a post, so I did some testing. It seems the image gets cut off, rather than resized. There is also no way of scrolling to see the image in the post itself.Your images may only be up to 1200 pixels wide.
Here's a demo:
The image is 1200px in width, but it is cut off.
The current maximum width of that specific portion of the forum is about 700px.
I would say the best solution is to modify the BBCode img tag to scale the image. I believe this is usually done by modifying the includes/bbcode.php file. Adding style="max-width: 100%;" appears to work.
Otherwise, I'm sure the 1200px value can be adjusted somewhere.