One way to make sure that things "always" (in theory) post the right way on a forum is to make sure that the phone is oriented the right way when taking the photo.
On an iPhone, etc - the home button should be to the right or to the bottom when you take the photo. If it's in the other 2 orientations, the photo will be upside down but may be corrected depending on where it's posted only IF where it's posted reads the "exif" information to find out the right orientation.
If it's photographed the right way to begin with, it should always be right side up - regardless of how smart the destination software is.
Android based cameras/phones will be similar but I don't have one here to test with to find out the proper orientations.