To reproduce enter a formula with a syntax error, like
\int_a^b x^{5x dx
and look at the preview. You will only see the code inside a box (plus additional commands added by wiki2jax.js). This is not helpful. Probably just removing noError.js from the configuration will allow the error messages to show up, which will help authors to find and correct the syntax errors in their formulas.

Version: unspecified
Severity: enhancement