MathML seems to almost always work for me but I found one page that rampant with errors that prevent MathML from working almost entirely. Please see:
Exhibit A -- View with MathML rendering enabled in your user preferences.
https://en.wikipedia.org/w/index.php?title=Action_(physics)&oldid=649419549
As you can hopefully see (I've tested in multiple browsers on multiple platforms), almost none of the equations render at all. I could not find a single cause or solution -- I tried many different changes and none showed much consistency. The best I can come up with for a cause is that many of these equations use slightly nonstandard (?) fonts like \varepsilon, \mathcal, \mathbf, etc and this combines with nonstandard punctuation (in or around the equation) in some way to cause issues, e.g. "<math>blah</math>." [note the period] or ":<math> [newline] blah [newline] </math>". Only issue with this explanation is that the problem is there even for the last few equations which don't all seem to have issues like that.
Regardless of the cause, the best and most consistent solution I found was to simply add empty brackets before the end of every math element, i.e. replace all "</math>" --> "{}</math>". Please see:
Exhibit B -- Fixed version with diff. Again, view with MathML enabled to see that the issue is corrected.
https://en.wikipedia.org/w/index.php?title=Action_(physics)&diff=673395237&oldid=649419549
Please let me know if you do not see the problems I described, or if you do and you have some better idea what is going on here. Thanks.
