Applied mathematician here. It’s pretty sad that the totality of the comments ignore the content of this post and deal with rendering the notation (and of course add to that this comment itself, which is meta-commentary on rendering, and doesn’t pertain to the content either).
It's one comment thread where people are mostly trying to get to the bottom of why it's happening so future readers can read the article and discuss its contents.
I don’t disagree (except that it was a one-comment thread, now it’s a two-comment thread).
For me (FF 57.0.3) the MathML is shown as source and is not rendered.
Deactivating uBlock Origin makes the page render fine for me in FF 57.0.1 on Ubuntu.