I would guess as above but with an additional line about the adjustment, such as
Remove fire resistance or
Add Daily power: Pants drop! (with description of power if it is new).
With something else that is completely whole cloth, I would guess that keeping the formatting simple and understandable, avoiding trying to overly-emulate any tradedress (don't attach a PDF that is meant to mimic a page from a WotC book, for example), should keep the thread and EN World in safe waters.
If anything comes too close to the line, we'll just not post it or allow a mod/admin to edit as they please. Certainly, a WotC employee can always report a post as necessary if something is beyond allowed but I am not a fan of the idea that it is easier to ask forgiveness than permission because, IME, often there is already damage done by that point as well as hurt feelings. We'll just try to stay out in front on doing this fairly and correctly and legally right from the get-go.
Good questions and thanks!