Hmmm interesting Threads find - if you don't put alt text on your images, they attempt to guess at what it is and add it for you - and it federates with the image.
It's not very confident in it's answer, always seem to be "Photo by {yourName} on {date}, may be an image of {noun}."
Always better to add your own. But for people who just aren't going to do it, I guess it's better than nothing.
