The slug strips out all special characters and replaces spaces with en dashes. The title used MathJax for formatting (raw text: Reactions of metals with $\ce{HCl}$, $\ce{H2SO4}$, $\ce{HNO3}$?
), so you can see where the ce
came from.
I'm not as concerned about the URL slug{*} as I am about the displayed title in Google/etc. Google shows the mathjax dollar signs, etc, which looks ugly.

One fix for this would be to limit mhchem in titles. This can be done either forcibly (i.e, make the devs block it), or by just discouraging it.
We can discourage it by:
- Editing it out of titles
- Letting users know by comments ("Please do not use mathjax in titles, it is discouraged [linky link]")
- Ask the devs to put a little popup when mhchem is detected in titles ("Mhchem is discouraged in titles, are you sure you want to use it?")
Note that I'm fine with mathjax in titles, just not the use of \ce
.
*That may be just me--I generally don't find any need for the slug. But I can see how others may find it useful.