Feature summary:
Formulas entered in Wikidata (for instance, defining formula) and Wikipedia (documented in https://en.wikipedia.org/wiki/Help:Displaying_a_formula) should support symbols which are bold, sans-serif, and italic.

Use case(s):
Variables representing tensors are typically typeset in bold, sans-serif, and italic.
This is done for instance in the famous physics book Graviation and recommended by ISO (ISO 80000-2:2019, page 24, item 2-18.19).
Example which would be improved: Formula for tensor product of two tensors.

Benefits:
This would allow typesetting of tensor variables in the recommended, customary form.

Possible solution:
MathJax supports the \mathbfsfit command which produces the desired typesetting.