dekaccho
asked:
Do you think a changeling could use shape-shifting magic without a horn? Say if it was broken off or if it was born without one if it was more of an "inner ability" sort of thing?

I think so, though accessing it would be significantly more difficult.  The way I see magic in the MLP universe is that it doesn’t come from the horn, the horn is merely a conduit through which unicorns, changelings, etc. focus it.  Without a horn it would be much harder to focus the magic naturally, but it could still be done either through a substitute conduit or through a lot of intense practice.