I already saw one question about tracing differentiation provide an example equation using LaTeX. As I would like to be able to copy examples straight to Mathematica this is somewhat of a complication. Should we encourage posting example equations as Mathematica code (where relevant)?
This is an important point. I have thought about this before the site was launched, and expected that some would oppose enabling LaTeX support for fear of too many non-pasteable equations.
I think LaTeX is very useful for explaining mathematical stuff, and we definitely need it here. But I agree that as soon as we start talking about code, everything should be present in Mathematica syntax too. If in addition to that there's also LaTeX, that's great, but let's encourage posting copyable code as well.
Example using only LaTeX that I might frown upon:
How do I solve $f''(x) + f(x) + 1 = 0$ with Mathematica?
The OP should type the equation in Mathematica syntax because people will want to copy it.
An example where I think LaTeX would be appropriate (and preferred):
The guideline should be: should anyone ever need to paste the equation, it must be given in Mathematica syntax as well (perhaps in addition to LaTeX if so desired)
I'd like to mention here that you can copy MathJax equations as MathML and paste into Mathematica directly as
TraditionalForm. This often needs some cleanup before Mathematica can interpret it correctly.
EDIT: It's always good to have particular examples. I do think LaTeX is appropriate in this post. People may very well want to use the equation in Mathematica form, but I think human-readability is more important in this case.
What I'd like to avoid is copying Mathematica expression as LaTeX, like here, when the emphasis is on how to do something techincal in Mathematica, and not on the mathematics.