I'm pretty new to MathJax, and one way I've been trying to learn is to click on "edit" for posts that use features I would like to learn. Then I just click "cancel." The last time I did this, I got a notice that my previous edit was rejected. The last time I intentionally edited a question, I know it was accepted, because I got 2 points or something like that, so I know this is something else.
Am I violating some rule, or did I just forget to click "Cancel"?
I do not see any problem in doing what you do.
The warning is just because you had an actual rejection of a suggested edit. But this was just bad luck; the edit itself seemed to make sense, so I assume it was intentional and not a by product of your practice. Maybe you just forgot about that one.
That said, if you "right-click" (or whatever is the equivalent action in your setup) on a formula, you get a menu and there you can select "show math as" and then TeX Commands. This often may be a more direct way to achieve what you want to do.
To be explicitly clear, there's no rule against doing this.
And clicking "edit" by itself doesn't have any effect on the post at all, and is not recorded anywhere (except in a server log somewhere that, in practice, nobody is likely to look at). So even if there were a rule against it, there would be no way for anyone on the site to find out that you broke that rule.
