I seem to have found an 'edge' case.
While 'CodeMirror' (e.g. syntax highlighting) works exceptionally well (SQL, Python, HTML, CSS tested so far) it just doesn't like 'UNION' for some reason as I get a blank white page with a 'FORBIDDEN' message. So I hit the 'back' button and add something before and after the 'UNION' and then it seems to be ok, for example:
SELECT * FROM riders WHERE total_trips < 500 -> UNION <- SELECT * FROM riders2 WHERE total_trips < 500;
I usually have the CODE in a DIV, which can sometimes can be in a FADE.
Oh, and all of this is typically in a FLUIDGRID...
Small workaround, but otherwise, CodeMirror work great!