If I click the text it opens an empty page pointing at the file with "No video with supported Format and MIME found". But if I expand it by clicking the symbol the video works. (that's the original link for this post...)
So I can sadly understand if less tech-inclined people complain about Firefox when something like this happens.
I think you don't need to mirror the file. Just putting the original link here already fixes it. Links directly pointing to the mp4 file seem to be handled differently than the link being embedded (and expanded by clicking the symbol) here (tested below)