This subject comes up fairly regularly, so here is the most probable explanation.
Photos in question are likely taken with a smart phone, and the forum software (and Microsoft Windows in general), do not play well with those photos.
This "problem" has existed (for several years) since Apple (and later other smart phone brands) OS started using the orientation tag in the JPG EXIF metadata to properly orient displayed photos.
https://www.howtogeek.com/254830/why-your-photos-dont-always-appear-correctly-rotated/Expanding further, this problem with wrong photo orientation (as explained in the link above) is not as much with the way you hold the phone, but it is in the way the phone saves the pixels in the JPG file. Instead of storing the pixels in the same orientation as they were captured by the image sensor, they store all the pixels in a fixed orientation (whatever it is) regardless of what the image sensor captured, then they add a tag in the EXIF part of the JPG file, instructing whatever rendering program is used to view them to rotate the stored pixels if needed.
The old way (which worked for many years) was to have the pixel data stored in the same orientation as they were captured by the image sensor, and not use any EXIF tags. Another example of making things more complicated than they should be. Why not just use the KISS principle?
This problem is not just on this forum -- I have seen it elsewhere too. And as far as editing (rotating) the photos goes, if you attached them to your post, nothing can be done. If you stored them in your TRW photo album, then can be edited and rotated, but IIRC, that doesn't seem to always work.
