\bmod does not work in Wikipedia's substitute for TeX. The "b" is supposed to mean "binary", and it should mean that the amount of space before and after "mod" is what is appropriate for a binary operator in mathematical notation. That space does not appear there.
Look at this section:
https://en.wikipedia.org/wiki/Dominical_letter#Formula_derived_from_Gauss.27s_algorithm
Following a discussion at https://en.wikipedia.org/wiki/Wikipedia_talk:WikiProject_Mathematics#.5Cbmod_does_not_work. it seems like this is an old bug with the texvc renderer. Hardy is using that setting for his preference. It works fine with the MathML/SVG renderer.
There might be a case to detect \bmod during parsing and substitute this with \,\bmod\, before being fed into texvc.