Allowing folks who've learned to edit on one site to do so with less friction on other sites is a really good idea.
That said, the big show-stopper here is the lack of editing guidance on the inline editor. In particular, site-specific items such as MathJax help would never be seen by folks who garnered sufficient reputation on a site without them, if the ...
I have good news and bad news.
The bad news is that this has been the case for a very long time so long as you had inline editing privileges.
The good news is that I'm pushing a fix to this for us inline editors. Should be live in rev 2014.4.4.2136 on meta and 2014.4.4.1527 elsewhere.
There is actually no check for the reputation level in the inline editor, so I made a simple script which allows you to edit inline regardless of reputation (doesn't even require to be logged in), which I already posted on Stack Apps.
// @name Always Edit Inline
// @version 1.0
// @description Adds an ability to lauch inline ...