The internet has become 3 massive multi-user blogs, each largely consisting of screenshots taken of the other two. This kind of blows, and not just for the usual reasons that may spring to mind.
Images are a terrible medium for online communication! Not everyone online uses a monitor. Any messages contained in a picture is straight up unacceptable without alt-text. It also makes it harder to find and fact check sources, or to spread a thought or idea further than yet another image upload. Copy/pasting text is just plain easier than downloading and uploading.
If you're going through the trouble of creating an image post, take an extra minuite to copy/past (or even transcribe) the source text into the alt-text submission. It's not much, but it goes a ways to improving how we use this blasted network!
https://uxdesign.cc/how-to-write-an-image-description-2f30d3bf5546
This doesn't work on mobile for me! Check my comment on the OP. At least with Fennec mobile
It works the way it's intended to work. If the text is for everyone just put it in the main text.