There is an older question about how to embed images, but it is out-of-date, the system currently goes right to the Imgur panel. When I try to use this to link to an image on the wiki commons, I get an error about it being the wrong format. The images are JPG or GIF, which strikes me as odd.
I suspect the error message is inaccurate, and it is some other problem. But how do I find out what's actually going on?
UPDATE: as requested... this happens all the time, on different images. In this particular case I...
- clicked the embed image button
- clicked "link from the web"
- pasted in https://en.wikipedia.org/wiki/Airfoil#/media/File:Lift_drag_graph.JPG
And then tried to post it. I also tried two other images from different web sites, but I am not sure which ones, it was some time ago now.