Wikimedia Bugzilla is closed!

f prime should look like an f followed by a mark that looks almost like an apostrophe. 
Instead, it looks like an f. See [[prime (mark)]] for an example of an unfixed f prime, 
about 4 lines from the top of the text. If you look sharp, you can see the prime stuck 
onto the top of the f, making the f's "hat" look a little longer than a normal f. 
(Assuming our fonts are compatible.) If you don't look sharp, it looks a lot more like 
an f than an f prime. That's as catastrophic to calculus as a + looking like a - would 
be to arithmetic. See [[derivative]], where I patched the problem by putting a space 
between the f and the prime, both in html format and in <math> format, although it 
doesn't look quite right. More f primes presumably exist throughout Wikipedia math 
articles, although I didn't find a good way to search for them.