The images are tagged with rotation data, but for whatever reason some software is ignoring it - BUT, it looks like it's only when presented through the forum software. For instance , Safari on OSX is displaying some images on their side, seemingly ignoring the tag, but if you view the image in its own window, it will display properly. Likewise if you drag the image to the desktop and then display it back in the browser (or Preview) you can see it displayed properly. Working fine in Safari in iOS 9.1
The images appearing on their side are tagged with an orientation of "6" which is 90 degrees Clockwise.
More info here:
ImpulseAdventure - JPEG / Exif Orientation and Rotation
The solution to posting images on the forum so that everyone can see them properly is to pre-rotate them in your photo software before uploading. This needs to erase the rotation tags and actually transform the pixels of the photo into the new orientation.