Have the fallback image rules been changed?

I see formulas on Wikipedia, using the Nook, without logging in.

@mobrovac I see the formula.

I do have Javascript enabled in both browsers.
hasFeature returns false in both browsers.
I'm unclear when the code from either of the github references is run.

I'm changing my story:

• When I'm given an SVG fallback image, the URL begins "https://en.wikipedia.org/", and I get a question mark icon.
• If I change "svg" to "png" in that URL, I get a formula displayed.
• When I'm given a PNG fallback image, the URL begins "//upload.wikimedia.org/". I did not forget to type "https:", it is not in the "src" attribute of the "img" element. If I insert "https:", or put a '<base href="https://en.wikipedia.org/">' in my test file, I get a formula displayed. It is distinctly different from the one displayed when I changed "svg" to "png" in item 2 above.

@Physikerwelt The Dolphin browser has a "save page" option. I don't trust it: I have seen a case where the text it saved was not what I saw when I viewed the source (innerHTML) of a page.

@Physikerwelt I don't know whether you mean edit the source sent to the browser or just try visiting the image file with a modified name. Either way, I don't have a real browser, I don't have a real Android tablet, I'm not in a position to copy/paste/edit the source sent to the browser.

The image delivered when I cannot see it comes from https://en.wikipedia.org/.../svg/...
The image delivered when I log in and set formula Preference to PNG comes from https://upload.wikimedia.org/math/...

The "formula" in Russell's paradox looks different now: there is a rectangular frame, about one text line high, about two thirds the width of the screen. In the center of the frame is a square icon showing a question mark. The icon looks familiar, so it might be what the browser displays when it is unable to load an image.