I am about to finalize the MathJax/mhchem 3.0.0 (which is quite a large update). To my knowledge, the largest user group can be found here. Would you mind if I put a link in the documentation to meta.chemistry.stackexchange.com and say that support for the mhchem syntax will be offered here? I will subscribe to the mhchem tag, of course.
The official documentation of MathJax/mhchem 3.0.0 can be found at https://mhchem.github.io/MathJax-mhchem/. It includes a test drive for live testing.
Please be aware that you might not be using the latest version. (Even StackExchange does not run the latest version, released just a couple of days ago.)
If you cannot find a solution there or with a web search, you might post your question here, at https://chemistry.meta.stackexchange.com/ with the
In my opinion, Chemistry.stackexchange.com is probably one of the largest (if not the single largest by a significant margin) sites to use MathJax with
mhchem. As such, it makes sense to offer documentation help here.
The caveat applies that you need five reputation points to ask/answer on meta. For most users of Stack Exchange, that is no problem, and most of the first-time posters on chemistry wouldn’t care anyway. Thus, the only people we cannot reach are those that use
mhchem, are not on SE, and do not have any chemistry questions to ask/answer. I would expect that group to be significantly small, though.
So yes, feel free to ask
mhchem support questions on here, they definitely benefit chem.SE users and may help keeping things in one place. But be prepared to open at least one other channel (e.g. e-mail) for people that do not use this site.