Board Thread:Support Requests - Getting Technical/@comment-24781490-20151223184531/@comment-1757994-20151223231257

MathML is currently only supported by Firefox, although Opera has supported it in the past. It's rather dependent on what fonts the user has installed, too.

MediaWiki's  tag invokes a display system derived from TeX. It does not implement full TeX (or full LaTeX). Wikia doesn't really maintain that, really, although if there's a bug, they'd probably try to fix it. Feature extensions are unlikely. Wikia's MediaWiki displays  as PNGs. (Wikipedia's  system supports MathML as an option, although it has some problems, too.)

For molecular diagrams, though, you need a graphics application. There are ones specifically for molecular diagrams, but I have no expertise there. It's highly unlikely that any of them would ever be integrated into MediaWiki.

Your best bet is probably to use an external app, maybe one that can generate graphics as SVGs, and upload the final images.