Probably this is known.

MathJax `\newcommand`

appears to be persistent
across the whole page, including the question + all answers.

This potentially might cause some mischief.

Trying to redefine `\mathbb`

in the answers.

Before redefinition: $\mathbb{N}$.

$\newcommand{mathbb}[1]{\text{;-) }#1}$

After: $\mathbb{N}$

`\mathbb{R}`

and or many`\operatorname{Ext}`

?! $\endgroup$`\newcommand\RR{\mathbb{R}}`

, another contains`\newcommand\RR{\mathcal{R}}`

, and a third uses`\RR`

without defining it, the symbol shown in the third answer depends on the order in which the previous answers are visualized? Sounds tricky. $\endgroup$